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 $87.72   7.127%   $93.9718   $93.97   $93.95   $94.00  
  Purchase #2 $122.82   9.512%   $134.5026   $134.50   $134.50   $134.50  
  Purchase #3 $200.33   7.700%   $215.7554   $215.76   $215.75   $215.80  
  Purchase #4 $245.77   3.733%   $254.9446   $254.94   $254.95   $254.90  
  Purchase #5 $72.85   5.221%   $76.6535   $76.65   $76.65   $76.70  
  Purchase #6 $199.88   11.478%   $222.8222   $222.82   $222.80   $222.80  
  Purchase #7 $34.72   4.119%   $36.1501   $36.15   $36.15   $36.20  
  7 purchase totals = $964.09       $1,034.8002   $1,034.79   $1,034.75   $1,034.90