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 $118.56   7.150%   $127.037   $127.04   $127.05   $127.00  
  Purchase #2 $247.33   5.765%   $261.5886   $261.59   $261.60   $261.60  
  Purchase #3 $214.86   11.627%   $239.8418   $239.84   $239.85   $239.80  
  Purchase #4 $237.33   9.368%   $259.5631   $259.56   $259.55   $259.60  
  Purchase #5 $151.53   12.386%   $170.2985   $170.30   $170.30   $170.30  
  Purchase #6 $205.50   3.757%   $213.2206   $213.22   $213.20   $213.20  
  Purchase #7 $200.77   4.838%   $210.4833   $210.48   $210.50   $210.50  
  7 purchase totals = $1,375.88       $1,482.0329   $1,482.03   $1,482.05   $1,482.00