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 $195.94   10.225%   $215.9749   $215.97   $215.95   $216.00  
  Purchase #2 $155.77   3.686%   $161.5117   $161.51   $161.50   $161.50  
  Purchase #3 $107.48   6.687%   $114.6672   $114.67   $114.65   $114.70  
  Purchase #4 $227.94   11.319%   $253.7405   $253.74   $253.75   $253.70  
  Purchase #5 $52.69   4.807%   $55.2228   $55.22   $55.20   $55.20  
  Purchase #6 $35.93   9.584%   $39.3735   $39.37   $39.35   $39.40  
  Purchase #7 $151.84   12.583%   $170.946   $170.95   $170.95   $170.90  
  7 purchase totals = $927.59       $1,011.4366   $1,011.43   $1,011.35   $1,011.40