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 $54.58   13.521%   $61.9598   $61.96   $61.95   $62.00  
  Purchase #2 $200.43   6.511%   $213.48   $213.48   $213.50   $213.50  
  Purchase #3 $165.70   9.863%   $182.043   $182.04   $182.05   $182.00  
  Purchase #4 $214.49   4.831%   $224.852   $224.85   $224.85   $224.90  
  Purchase #5 $168.77   5.683%   $178.3612   $178.36   $178.35   $178.40  
  Purchase #6 $102.57   9.585%   $112.4013   $112.40   $112.40   $112.40  
  Purchase #7 $199.95   7.725%   $215.3961   $215.40   $215.40   $215.40  
  7 purchase totals = $1,106.49       $1,188.4934   $1,188.49   $1,188.50   $1,188.60