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 $85.36   10.763%   $94.5473   $94.55   $94.55   $94.50  
  Purchase #2 $228.36   11.693%   $255.0621   $255.06   $255.05   $255.10  
  Purchase #3 $125.51   7.562%   $135.0011   $135.00   $135.00   $135.00  
  Purchase #4 $27.34   9.590%   $29.9619   $29.96   $29.95   $30.00  
  Purchase #5 $248.67   5.534%   $262.4314   $262.43   $262.45   $262.40  
  Purchase #6 $161.50   11.390%   $179.8949   $179.89   $179.90   $179.90  
  Purchase #7 $45.55   4.165%   $47.4472   $47.45   $47.45   $47.40  
  7 purchase totals = $922.29       $1,004.3459   $1,004.34   $1,004.35   $1,004.30