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 $216.66   9.471%   $237.1799   $237.18   $237.20   $237.20  
  Purchase #2 $227.62   10.672%   $251.9116   $251.91   $251.90   $251.90  
  Purchase #3 $242.67   9.517%   $265.7649   $265.76   $265.75   $265.80  
  Purchase #4 $142.25   4.677%   $148.903   $148.90   $148.90   $148.90  
  Purchase #5 $11.44   8.614%   $12.4254   $12.43   $12.45   $12.40  
  Purchase #6 $152.71   3.397%   $157.8976   $157.90   $157.90   $157.90  
  Purchase #7 $192.91   4.394%   $201.3865   $201.39   $201.40   $201.40  
  7 purchase totals = $1,186.26       $1,275.4689   $1,275.47   $1,275.50   $1,275.50