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 $197.80   8.166%   $213.9523   $213.95   $213.95   $214.00  
  Purchase #2 $79.61   11.733%   $88.9506   $88.95   $88.95   $89.00  
  Purchase #3 $46.26   9.565%   $50.6848   $50.68   $50.70   $50.70  
  Purchase #4 $224.87   12.663%   $253.3453   $253.35   $253.35   $253.30  
  Purchase #5 $169.40   13.821%   $192.8128   $192.81   $192.80   $192.80  
  Purchase #6 $179.83   7.107%   $192.6105   $192.61   $192.60   $192.60  
  Purchase #7 $118.83   5.389%   $125.2337   $125.23   $125.25   $125.20  
  7 purchase totals = $1,016.60       $1,117.5900   $1,117.58   $1,117.60   $1,117.60