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 $88.38   7.445%   $94.9599   $94.96   $94.95   $95.00  
  Purchase #2 $51.48   13.404%   $58.3804   $58.38   $58.40   $58.40  
  Purchase #3 $187.71   5.797%   $198.5915   $198.59   $198.60   $198.60  
  Purchase #4 $165.95   7.120%   $177.7656   $177.77   $177.75   $177.80  
  Purchase #5 $49.45   9.140%   $53.9697   $53.97   $53.95   $54.00  
  Purchase #6 $202.27   7.633%   $217.7093   $217.71   $217.70   $217.70  
  Purchase #7 $112.57   11.190%   $125.1666   $125.17   $125.15   $125.20  
  7 purchase totals = $857.81       $926.5430   $926.55   $926.50   $926.70