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 $198.60   3.710%   $205.9681   $205.97   $205.95   $206.00  
  Purchase #2 $52.75   6.527%   $56.193   $56.19   $56.20   $56.20  
  Purchase #3 $117.88   8.152%   $127.4896   $127.49   $127.50   $127.50  
  Purchase #4 $131.85   13.550%   $149.7157   $149.72   $149.70   $149.70  
  Purchase #5 $195.43   7.608%   $210.2983   $210.30   $210.30   $210.30  
  Purchase #6 $234.54   10.606%   $259.4153   $259.42   $259.40   $259.40  
  Purchase #7 $54.93   10.296%   $60.5856   $60.59   $60.60   $60.60  
  7 purchase totals = $985.98       $1,069.6656   $1,069.68   $1,069.65   $1,069.70