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 $196.97   8.839%   $214.3802   $214.38   $214.40   $214.40  
  Purchase #2 $152.37   3.386%   $157.5292   $157.53   $157.55   $157.50  
  Purchase #3 $240.94   4.245%   $251.1679   $251.17   $251.15   $251.20  
  Purchase #4 $24.36   11.451%   $27.1495   $27.15   $27.15   $27.10  
  Purchase #5 $182.44   12.362%   $204.9932   $204.99   $205.00   $205.00  
  Purchase #6 $157.82   10.778%   $174.8298   $174.83   $174.85   $174.80  
  Purchase #7 $7.42   3.160%   $7.6545   $7.65   $7.65   $7.70  
  7 purchase totals = $962.32       $1,037.7043   $1,037.70   $1,037.75   $1,037.70