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 $196.52   5.457%   $207.2441   $207.24   $207.25   $207.20  
  Purchase #2 $241.61   7.510%   $259.7549   $259.75   $259.75   $259.80  
  Purchase #3 $28.36   13.208%   $32.1058   $32.11   $32.10   $32.10  
  Purchase #4 $195.65   10.322%   $215.845   $215.85   $215.85   $215.80  
  Purchase #5 $83.61   11.318%   $93.073   $93.07   $93.05   $93.10  
  Purchase #6 $249.52   10.567%   $275.8868   $275.89   $275.90   $275.90  
  Purchase #7 $18.36   10.102%   $20.2147   $20.21   $20.20   $20.20  
  7 purchase totals = $1,013.63       $1,104.1243   $1,104.12   $1,104.10   $1,104.10