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 $95.46   11.309%   $106.2556   $106.26   $106.25   $106.30  
  Purchase #2 $63.34   8.292%   $68.5922   $68.59   $68.60   $68.60  
  Purchase #3 $216.41   9.151%   $236.2137   $236.21   $236.20   $236.20  
  Purchase #4 $91.83   5.864%   $97.2149   $97.21   $97.20   $97.20  
  Purchase #5 $242.86   5.601%   $256.4626   $256.46   $256.45   $256.50  
  Purchase #6 $248.45   9.297%   $271.5484   $271.55   $271.55   $271.50  
  Purchase #7 $103.49   12.477%   $116.4024   $116.40   $116.40   $116.40  
  7 purchase totals = $1,061.84       $1,152.6898   $1,152.68   $1,152.65   $1,152.70