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 $197.37   8.553%   $214.2511   $214.25   $214.25   $214.30  
  Purchase #2 $178.49   6.658%   $190.3739   $190.37   $190.35   $190.40  
  Purchase #3 $158.78   8.532%   $172.3271   $172.33   $172.35   $172.30  
  Purchase #4 $249.63   12.170%   $280.01   $280.01   $280.00   $280.00  
  Purchase #5 $115.93   12.385%   $130.2879   $130.29   $130.30   $130.30  
  Purchase #6 $161.56   7.165%   $173.1358   $173.14   $173.15   $173.10  
  Purchase #7 $44.50   3.821%   $46.2003   $46.20   $46.20   $46.20  
  7 purchase totals = $1,106.26       $1,206.5861   $1,206.59   $1,206.60   $1,206.60