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 $95.41   9.739%   $104.702   $104.70   $104.70   $104.70  
  Purchase #2 $91.49   5.551%   $96.5686   $96.57   $96.55   $96.60  
  Purchase #3 $139.46   7.713%   $150.2165   $150.22   $150.20   $150.20  
  Purchase #4 $61.35   4.796%   $64.2923   $64.29   $64.30   $64.30  
  Purchase #5 $112.61   5.791%   $119.1312   $119.13   $119.15   $119.10  
  Purchase #6 $67.43   13.790%   $76.7286   $76.73   $76.75   $76.70  
  Purchase #7 $64.66   11.360%   $72.0054   $72.01   $72.00   $72.00  
  7 purchase totals = $632.41       $683.6446   $683.65   $683.65   $683.60