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 $89.94   7.325%   $96.5281   $96.53   $96.55   $96.50  
  Purchase #2 $85.41   8.413%   $92.5955   $92.60   $92.60   $92.60  
  Purchase #3 $40.92   8.353%   $44.338   $44.34   $44.35   $44.30  
  Purchase #4 $115.57   10.443%   $127.639   $127.64   $127.65   $127.60  
  Purchase #5 $174.95   11.608%   $195.2582   $195.26   $195.25   $195.30  
  Purchase #6 $237.54   12.129%   $266.3512   $266.35   $266.35   $266.40  
  Purchase #7 $236.65   6.296%   $251.5495   $251.55   $251.55   $251.50  
  7 purchase totals = $980.98       $1,074.2595   $1,074.27   $1,074.30   $1,074.20