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 $67.69   12.507%   $76.156   $76.16   $76.15   $76.20  
  Purchase #2 $249.27   5.124%   $262.0426   $262.04   $262.05   $262.00  
  Purchase #3 $94.27   3.822%   $97.873   $97.87   $97.85   $97.90  
  Purchase #4 $192.42   5.178%   $202.3835   $202.38   $202.40   $202.40  
  Purchase #5 $245.91   12.198%   $275.9061   $275.91   $275.90   $275.90  
  Purchase #6 $101.73   8.504%   $110.3811   $110.38   $110.40   $110.40  
  Purchase #7 $67.69   7.811%   $72.9773   $72.98   $73.00   $73.00  
  7 purchase totals = $1,018.98       $1,097.7196   $1,097.72   $1,097.75   $1,097.80