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 $210.49   5.282%   $221.6081   $221.61   $221.60   $221.60  
  Purchase #2 $183.94   3.620%   $190.5986   $190.60   $190.60   $190.60  
  Purchase #3 $149.77   9.845%   $164.5149   $164.51   $164.50   $164.50  
  Purchase #4 $30.40   8.579%   $33.008   $33.01   $33.00   $33.00  
  Purchase #5 $197.76   8.833%   $215.2281   $215.23   $215.25   $215.20  
  Purchase #6 $119.50   11.425%   $133.1529   $133.15   $133.15   $133.20  
  Purchase #7 $191.83   13.182%   $217.117   $217.12   $217.10   $217.10  
  7 purchase totals = $1,083.69       $1,175.2276   $1,175.23   $1,175.20   $1,175.20