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 $119.54   4.734%   $125.199   $125.20   $125.20   $125.20  
  Purchase #2 $159.56   5.841%   $168.8799   $168.88   $168.90   $168.90  
  Purchase #3 $129.93   6.652%   $138.5729   $138.57   $138.55   $138.60  
  Purchase #4 $177.43   11.618%   $198.0438   $198.04   $198.05   $198.00  
  Purchase #5 $204.75   11.812%   $228.9351   $228.94   $228.95   $228.90  
  Purchase #6 $13.98   3.864%   $14.5202   $14.52   $14.50   $14.50  
  Purchase #7 $63.34   9.218%   $69.1787   $69.18   $69.20   $69.20  
  7 purchase totals = $868.53       $943.3296   $943.33   $943.35   $943.30