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 $48.44   10.684%   $53.6153   $53.62   $53.60   $53.60  
  Purchase #2 $23.26   11.525%   $25.9407   $25.94   $25.95   $25.90  
  Purchase #3 $56.36   10.794%   $62.4435   $62.44   $62.45   $62.40  
  Purchase #4 $121.53   4.584%   $127.1009   $127.10   $127.10   $127.10  
  Purchase #5 $208.47   4.829%   $218.537   $218.54   $218.55   $218.50  
  Purchase #6 $244.55   13.152%   $276.7132   $276.71   $276.70   $276.70  
  Purchase #7 $202.87   5.103%   $213.2225   $213.22   $213.20   $213.20  
  7 purchase totals = $905.48       $977.5731   $977.57   $977.55   $977.40