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 $195.66   3.856%   $203.2046   $203.20   $203.20   $203.20  
  Purchase #2 $198.74   8.352%   $215.3388   $215.34   $215.35   $215.30  
  Purchase #3 $99.53   3.818%   $103.3301   $103.33   $103.35   $103.30  
  Purchase #4 $148.77   3.492%   $153.965   $153.97   $153.95   $154.00  
  Purchase #5 $168.51   10.198%   $185.6946   $185.69   $185.70   $185.70  
  Purchase #6 $48.53   10.554%   $53.6519   $53.65   $53.65   $53.70  
  Purchase #7 $135.99   13.596%   $154.4792   $154.48   $154.50   $154.50  
  7 purchase totals = $995.73       $1,069.6642   $1,069.66   $1,069.70   $1,069.70