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 $68.40   5.707%   $72.3036   $72.30   $72.30   $72.30  
  Purchase #2 $220.61   6.392%   $234.7114   $234.71   $234.70   $234.70  
  Purchase #3 $100.66   10.228%   $110.9555   $110.96   $110.95   $111.00  
  Purchase #4 $119.50   4.589%   $124.9839   $124.98   $125.00   $125.00  
  Purchase #5 $40.96   10.191%   $45.1342   $45.13   $45.15   $45.10  
  Purchase #6 $157.83   7.385%   $169.4857   $169.49   $169.50   $169.50  
  Purchase #7 $182.66   3.430%   $188.9252   $188.93   $188.95   $188.90  
  7 purchase totals = $890.62       $946.4995   $946.50   $946.55   $946.50