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 $24.35   4.828%   $25.5256   $25.53   $25.55   $25.50  
  Purchase #2 $68.80   9.589%   $75.3972   $75.40   $75.40   $75.40  
  Purchase #3 $213.82   13.318%   $242.2965   $242.30   $242.30   $242.30  
  Purchase #4 $104.51   5.631%   $110.395   $110.40   $110.40   $110.40  
  Purchase #5 $237.51   7.286%   $254.815   $254.82   $254.80   $254.80  
  Purchase #6 $152.64   6.121%   $161.9831   $161.98   $162.00   $162.00  
  Purchase #7 $244.38   3.633%   $253.2583   $253.26   $253.25   $253.30  
  7 purchase totals = $1,046.01       $1,123.6707   $1,123.69   $1,123.70   $1,123.70