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 $195.96   5.695%   $207.1199   $207.12   $207.10   $207.10  
  Purchase #2 $78.71   6.140%   $83.5428   $83.54   $83.55   $83.50  
  Purchase #3 $12.33   10.590%   $13.6357   $13.64   $13.65   $13.60  
  Purchase #4 $30.51   10.570%   $33.7349   $33.73   $33.75   $33.70  
  Purchase #5 $119.44   11.399%   $133.055   $133.06   $133.05   $133.10  
  Purchase #6 $203.28   6.804%   $217.1112   $217.11   $217.10   $217.10  
  Purchase #7 $70.75   4.420%   $73.8772   $73.88   $73.90   $73.90  
  7 purchase totals = $710.98       $762.0767   $762.08   $762.10   $762.00