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 $191.73   5.292%   $201.8764   $201.88   $201.90   $201.90  
  Purchase #2 $211.70   13.447%   $240.1673   $240.17   $240.15   $240.20  
  Purchase #3 $79.60   3.337%   $82.2563   $82.26   $82.25   $82.30  
  Purchase #4 $14.71   7.543%   $15.8196   $15.82   $15.80   $15.80  
  Purchase #5 $207.53   4.588%   $217.0515   $217.05   $217.05   $217.10  
  Purchase #6 $101.57   9.192%   $110.9063   $110.91   $110.90   $110.90  
  Purchase #7 $129.35   13.138%   $146.344   $146.34   $146.35   $146.30  
  7 purchase totals = $936.19       $1,014.4214   $1,014.43   $1,014.40   $1,014.50