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 $58.25   7.744%   $62.7609   $62.76   $62.75   $62.80  
  Purchase #2 $20.98   7.496%   $22.5527   $22.55   $22.55   $22.60  
  Purchase #3 $101.75   12.739%   $114.7119   $114.71   $114.70   $114.70  
  Purchase #4 $114.92   9.625%   $125.9811   $125.98   $126.00   $126.00  
  Purchase #5 $185.42   6.228%   $196.968   $196.97   $196.95   $197.00  
  Purchase #6 $170.28   5.485%   $179.6199   $179.62   $179.60   $179.60  
  Purchase #7 $46.51   8.450%   $50.4401   $50.44   $50.45   $50.40  
  7 purchase totals = $698.11       $753.0346   $753.03   $753.00   $753.10