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 $83.26   11.200%   $92.5851   $92.59   $92.60   $92.60  
  Purchase #2 $49.34   4.668%   $51.6432   $51.64   $51.65   $51.60  
  Purchase #3 $240.63   3.548%   $249.1676   $249.17   $249.15   $249.20  
  Purchase #4 $239.90   7.591%   $258.1108   $258.11   $258.10   $258.10  
  Purchase #5 $131.37   4.568%   $137.371   $137.37   $137.35   $137.40  
  Purchase #6 $31.38   12.352%   $35.2561   $35.26   $35.25   $35.30  
  Purchase #7 $247.41   9.233%   $270.2534   $270.25   $270.25   $270.30  
  7 purchase totals = $1,023.29       $1,094.3872   $1,094.39   $1,094.35   $1,094.50