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 $84.29   12.736%   $95.0252   $95.03   $95.05   $95.00  
  Purchase #2 $70.50   7.234%   $75.6   $75.60   $75.60   $75.60  
  Purchase #3 $79.72   4.195%   $83.0643   $83.06   $83.05   $83.10  
  Purchase #4 $202.69   5.777%   $214.3994   $214.40   $214.40   $214.40  
  Purchase #5 $107.73   7.687%   $116.0112   $116.01   $116.00   $116.00  
  Purchase #6 $163.29   7.283%   $175.1824   $175.18   $175.20   $175.20  
  Purchase #7 $158.75   4.735%   $166.2668   $166.27   $166.25   $166.30  
  7 purchase totals = $866.97       $925.5493   $925.55   $925.55   $925.60