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 $45.40   5.566%   $47.927   $47.93   $47.95   $47.90  
  Purchase #2 $118.94   12.865%   $134.2416   $134.24   $134.25   $134.20  
  Purchase #3 $112.67   11.247%   $125.342   $125.34   $125.35   $125.30  
  Purchase #4 $201.25   3.501%   $208.2958   $208.30   $208.30   $208.30  
  Purchase #5 $55.37   9.481%   $60.6196   $60.62   $60.60   $60.60  
  Purchase #6 $240.31   5.784%   $254.2095   $254.21   $254.20   $254.20  
  Purchase #7 $94.87   4.255%   $98.9067   $98.91   $98.90   $98.90  
  7 purchase totals = $868.81       $929.5422   $929.55   $929.55   $929.40