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 $241.53   8.483%   $262.019   $262.02   $262.00   $262.00  
  Purchase #2 $172.34   3.768%   $178.8338   $178.83   $178.85   $178.80  
  Purchase #3 $81.29   12.141%   $91.1594   $91.16   $91.15   $91.20  
  Purchase #4 $68.38   11.861%   $76.4906   $76.49   $76.50   $76.50  
  Purchase #5 $180.86   10.244%   $199.3873   $199.39   $199.40   $199.40  
  Purchase #6 $87.28   12.491%   $98.1821   $98.18   $98.20   $98.20  
  Purchase #7 $170.99   5.829%   $180.957   $180.96   $180.95   $181.00  
  7 purchase totals = $1,002.67       $1,087.0292   $1,087.03   $1,087.05   $1,087.10