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 $88.37   7.858%   $95.3141   $95.31   $95.30   $95.30  
  Purchase #2 $166.90   9.302%   $182.425   $182.43   $182.45   $182.40  
  Purchase #3 $97.84   5.341%   $103.0656   $103.07   $103.05   $103.10  
  Purchase #4 $228.31   7.686%   $245.8579   $245.86   $245.85   $245.90  
  Purchase #5 $76.29   13.244%   $86.3938   $86.39   $86.40   $86.40  
  Purchase #6 $115.37   12.463%   $129.7486   $129.75   $129.75   $129.70  
  Purchase #7 $119.28   3.191%   $123.0862   $123.09   $123.10   $123.10  
  7 purchase totals = $892.36       $965.8912   $965.90   $965.90   $965.90