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 $41.51   11.241%   $46.1761   $46.18   $46.20   $46.20  
  Purchase #2 $151.40   7.779%   $163.1774   $163.18   $163.20   $163.20  
  Purchase #3 $188.45   5.568%   $198.9429   $198.94   $198.95   $198.90  
  Purchase #4 $82.93   13.318%   $93.9746   $93.97   $93.95   $94.00  
  Purchase #5 $192.50   8.689%   $209.2263   $209.23   $209.25   $209.20  
  Purchase #6 $163.25   11.329%   $181.7446   $181.74   $181.75   $181.70  
  Purchase #7 $216.90   10.193%   $239.0086   $239.01   $239.00   $239.00  
  7 purchase totals = $1,036.94       $1,132.2505   $1,132.25   $1,132.30   $1,132.20