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 $59.67   4.132%   $62.1356   $62.14   $62.15   $62.10  
  Purchase #2 $205.66   11.568%   $229.4507   $229.45   $229.45   $229.50  
  Purchase #3 $38.87   3.450%   $40.211   $40.21   $40.20   $40.20  
  Purchase #4 $31.76   5.486%   $33.5024   $33.50   $33.50   $33.50  
  Purchase #5 $193.36   11.753%   $216.0856   $216.09   $216.10   $216.10  
  Purchase #6 $209.29   12.263%   $234.9552   $234.96   $234.95   $235.00  
  Purchase #7 $199.73   12.636%   $224.9679   $224.97   $224.95   $225.00  
  7 purchase totals = $938.34       $1,041.3084   $1,041.32   $1,041.30   $1,041.40