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 $87.40   8.466%   $94.7993   $94.80   $94.80   $94.80  
  Purchase #2 $10.43   5.650%   $11.0193   $11.02   $11.00   $11.00  
  Purchase #3 $57.26   4.725%   $59.9655   $59.97   $59.95   $60.00  
  Purchase #4 $143.90   6.711%   $153.5571   $153.56   $153.55   $153.60  
  Purchase #5 $186.57   3.534%   $193.1634   $193.16   $193.15   $193.20  
  Purchase #6 $110.73   13.143%   $125.2832   $125.28   $125.30   $125.30  
  Purchase #7 $219.69   5.215%   $231.1468   $231.15   $231.15   $231.10  
  7 purchase totals = $815.98       $868.9346   $868.94   $868.90   $869.00