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 $117.32   6.767%   $125.259   $125.26   $125.25   $125.30  
  Purchase #2 $157.53   13.294%   $178.472   $178.47   $178.45   $178.50  
  Purchase #3 $178.66   11.117%   $198.5216   $198.52   $198.50   $198.50  
  Purchase #4 $221.29   5.724%   $233.9566   $233.96   $233.95   $234.00  
  Purchase #5 $200.91   6.175%   $213.3162   $213.32   $213.30   $213.30  
  Purchase #6 $53.74   13.348%   $60.9132   $60.91   $60.90   $60.90  
  Purchase #7 $32.63   4.726%   $34.1721   $34.17   $34.15   $34.20  
  7 purchase totals = $962.08       $1,044.6107   $1,044.61   $1,044.50   $1,044.70