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 $58.79   5.501%   $62.024   $62.02   $62.00   $62.00  
  Purchase #2 $7.58   8.379%   $8.2151   $8.22   $8.20   $8.20  
  Purchase #3 $20.58   9.168%   $22.4668   $22.47   $22.45   $22.50  
  Purchase #4 $94.33   7.654%   $101.55   $101.55   $101.55   $101.60  
  Purchase #5 $13.63   3.684%   $14.1321   $14.13   $14.15   $14.10  
  Purchase #6 $108.95   9.422%   $119.2153   $119.22   $119.20   $119.20  
  Purchase #7 $166.79   13.483%   $189.2783   $189.28   $189.30   $189.30  
  7 purchase totals = $470.65       $516.8816   $516.89   $516.85   $516.90