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 $102.89   10.762%   $113.963   $113.96   $113.95   $114.00  
  Purchase #2 $64.69   12.134%   $72.5395   $72.54   $72.55   $72.50  
  Purchase #3 $149.37   5.781%   $158.0051   $158.01   $158.00   $158.00  
  Purchase #4 $193.49   11.652%   $216.0355   $216.04   $216.05   $216.00  
  Purchase #5 $9.89   5.370%   $10.4211   $10.42   $10.40   $10.40  
  Purchase #6 $146.73   11.461%   $163.5467   $163.55   $163.55   $163.50  
  Purchase #7 $211.36   5.546%   $223.082   $223.08   $223.10   $223.10  
  7 purchase totals = $878.42       $957.5929   $957.60   $957.60   $957.50