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 $46.50   3.376%   $48.0698   $48.07   $48.05   $48.10  
  Purchase #2 $119.99   5.250%   $126.2895   $126.29   $126.30   $126.30  
  Purchase #3 $129.36   3.507%   $133.8967   $133.90   $133.90   $133.90  
  Purchase #4 $215.40   13.762%   $245.0433   $245.04   $245.05   $245.00  
  Purchase #5 $211.62   11.746%   $236.4769   $236.48   $236.50   $236.50  
  Purchase #6 $49.47   11.202%   $55.0116   $55.01   $55.00   $55.00  
  Purchase #7 $193.99   4.709%   $203.125   $203.13   $203.15   $203.10  
  7 purchase totals = $966.33       $1,047.9128   $1,047.92   $1,047.95   $1,047.90