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 $187.84   7.265%   $201.4866   $201.49   $201.50   $201.50  
  Purchase #2 $212.99   7.739%   $229.4733   $229.47   $229.45   $229.50  
  Purchase #3 $112.98   9.610%   $123.8374   $123.84   $123.85   $123.80  
  Purchase #4 $167.65   3.736%   $173.9134   $173.91   $173.90   $173.90  
  Purchase #5 $67.98   3.187%   $70.1465   $70.15   $70.15   $70.10  
  Purchase #6 $199.76   4.739%   $209.2266   $209.23   $209.25   $209.20  
  Purchase #7 $50.56   8.304%   $54.7585   $54.76   $54.75   $54.80  
  7 purchase totals = $999.76       $1,062.8423   $1,062.85   $1,062.85   $1,062.80