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 $110.62   13.541%   $125.5991   $125.60   $125.60   $125.60  
  Purchase #2 $221.70   8.785%   $241.1763   $241.18   $241.20   $241.20  
  Purchase #3 $240.84   10.860%   $266.9952   $267.00   $267.00   $267.00  
  Purchase #4 $59.87   10.248%   $66.0055   $66.01   $66.00   $66.00  
  Purchase #5 $211.70   11.549%   $236.1492   $236.15   $236.15   $236.10  
  Purchase #6 $161.89   9.642%   $177.4994   $177.50   $177.50   $177.50  
  Purchase #7 $56.30   6.485%   $59.9511   $59.95   $59.95   $60.00  
  7 purchase totals = $1,062.92       $1,173.3758   $1,173.39   $1,173.40   $1,173.40