Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $94.91   13.750%   $107.9601   $107.96   $107.95   $108.00  
  Purchase #2 $227.75   8.682%   $247.5233   $247.52   $247.50   $247.50  
  Purchase #3 $150.29   4.151%   $156.5285   $156.53   $156.55   $156.50  
  Purchase #4 $84.94   5.136%   $89.3025   $89.30   $89.30   $89.30  
  Purchase #5 $247.32   7.415%   $265.6588   $265.66   $265.65   $265.70  
  Purchase #6 $202.41   11.313%   $225.3086   $225.31   $225.30   $225.30  
  Purchase #7 $110.52   7.346%   $118.6388   $118.64   $118.65   $118.60  
  7 purchase totals = $1,118.14       $1,210.9206   $1,210.92   $1,210.90   $1,210.90