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 $94.53   11.128%   $105.0493   $105.05   $105.05   $105.00  
  Purchase #2 $195.99   10.604%   $216.7728   $216.77   $216.75   $216.80  
  Purchase #3 $241.99   3.132%   $249.5691   $249.57   $249.55   $249.60  
  Purchase #4 $237.65   7.469%   $255.4001   $255.40   $255.40   $255.40  
  Purchase #5 $60.68   3.378%   $62.7298   $62.73   $62.75   $62.70  
  Purchase #6 $44.34   3.661%   $45.9633   $45.96   $45.95   $46.00  
  Purchase #7 $64.33   11.455%   $71.699   $71.70   $71.70   $71.70  
  7 purchase totals = $939.51       $1,007.1834   $1,007.18   $1,007.15   $1,007.20