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 $60.32   3.506%   $62.4348   $62.43   $62.45   $62.40  
  Purchase #2 $39.93   12.750%   $45.0211   $45.02   $45.00   $45.00  
  Purchase #3 $23.89   7.550%   $25.6937   $25.69   $25.70   $25.70  
  Purchase #4 $250.27   4.246%   $260.8965   $260.90   $260.90   $260.90  
  Purchase #5 $132.66   10.572%   $146.6848   $146.68   $146.70   $146.70  
  Purchase #6 $22.58   6.106%   $23.9587   $23.96   $23.95   $24.00  
  Purchase #7 $153.71   9.143%   $167.7637   $167.76   $167.75   $167.80  
  7 purchase totals = $683.36       $732.4533   $732.44   $732.45   $732.50