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 $84.85   8.700%   $92.232   $92.23   $92.25   $92.20  
  Purchase #2 $99.89   10.157%   $110.0358   $110.04   $110.05   $110.00  
  Purchase #3 $44.65   3.615%   $46.2641   $46.26   $46.25   $46.30  
  Purchase #4 $191.96   13.389%   $217.6615   $217.66   $217.65   $217.70  
  Purchase #5 $178.80   3.833%   $185.6534   $185.65   $185.65   $185.70  
  Purchase #6 $114.42   9.460%   $125.2441   $125.24   $125.25   $125.20  
  Purchase #7 $246.53   3.790%   $255.8735   $255.87   $255.85   $255.90  
  7 purchase totals = $961.10       $1,032.9644   $1,032.95   $1,032.95   $1,033.00