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 $52.66   4.817%   $55.1966   $55.20   $55.20   $55.20  
  Purchase #2 $201.30   10.662%   $222.7626   $222.76   $222.75   $222.80  
  Purchase #3 $12.35   13.399%   $14.0048   $14.00   $14.00   $14.00  
  Purchase #4 $243.31   3.137%   $250.9426   $250.94   $250.95   $250.90  
  Purchase #5 $234.74   4.381%   $245.024   $245.02   $245.00   $245.00  
  Purchase #6 $70.84   7.752%   $76.3315   $76.33   $76.35   $76.30  
  Purchase #7 $61.69   11.587%   $68.838   $68.84   $68.85   $68.80  
  7 purchase totals = $876.89       $933.1001   $933.09   $933.10   $933.00