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 $76.47   12.429%   $85.9745   $85.97   $85.95   $86.00  
  Purchase #2 $233.54   12.612%   $262.9941   $262.99   $263.00   $263.00  
  Purchase #3 $119.83   4.763%   $125.5375   $125.54   $125.55   $125.50  
  Purchase #4 $168.32   9.489%   $184.2919   $184.29   $184.30   $184.30  
  Purchase #5 $109.95   5.833%   $116.3634   $116.36   $116.35   $116.40  
  Purchase #6 $194.67   12.235%   $218.4879   $218.49   $218.50   $218.50  
  Purchase #7 $195.86   12.529%   $220.3993   $220.40   $220.40   $220.40  
  7 purchase totals = $1,098.64       $1,214.0486   $1,214.04   $1,214.05   $1,214.10