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 $69.48   5.451%   $73.2674   $73.27   $73.25   $73.30  
  Purchase #2 $188.73   5.451%   $199.0177   $199.02   $199.00   $199.00  
  Purchase #3 $190.37   11.736%   $212.7118   $212.71   $212.70   $212.70  
  Purchase #4 $51.45   6.712%   $54.9033   $54.90   $54.90   $54.90  
  Purchase #5 $44.29   3.779%   $45.9637   $45.96   $45.95   $46.00  
  Purchase #6 $99.75   4.541%   $104.2796   $104.28   $104.30   $104.30  
  Purchase #7 $216.44   12.173%   $242.7872   $242.79   $242.80   $242.80  
  7 purchase totals = $860.51       $932.9307   $932.93   $932.90   $933.00