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 $83.91   12.671%   $94.5422   $94.54   $94.55   $94.50  
  Purchase #2 $139.67   6.204%   $148.3351   $148.34   $148.35   $148.30  
  Purchase #3 $161.70   9.808%   $177.5595   $177.56   $177.55   $177.60  
  Purchase #4 $199.29   12.709%   $224.6178   $224.62   $224.60   $224.60  
  Purchase #5 $103.91   11.660%   $116.0259   $116.03   $116.05   $116.00  
  Purchase #6 $205.48   6.594%   $219.0294   $219.03   $219.05   $219.00  
  Purchase #7 $201.43   7.809%   $217.1597   $217.16   $217.15   $217.20  
  7 purchase totals = $1,095.39       $1,197.2696   $1,197.28   $1,197.30   $1,197.20