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 $214.76   8.347%   $232.686   $232.69   $232.70   $232.70  
  Purchase #2 $109.38   9.381%   $119.6409   $119.64   $119.65   $119.60  
  Purchase #3 $90.30   4.366%   $94.2425   $94.24   $94.25   $94.20  
  Purchase #4 $63.79   6.804%   $68.1303   $68.13   $68.15   $68.10  
  Purchase #5 $44.43   4.376%   $46.3743   $46.37   $46.35   $46.40  
  Purchase #6 $162.86   7.319%   $174.7797   $174.78   $174.80   $174.80  
  Purchase #7 $78.59   13.155%   $88.9285   $88.93   $88.95   $88.90  
  7 purchase totals = $764.11       $824.7822   $824.78   $824.85   $824.70