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 $83.82   13.661%   $95.2707   $95.27   $95.25   $95.30  
  Purchase #2 $187.47   6.453%   $199.5674   $199.57   $199.55   $199.60  
  Purchase #3 $104.40   12.790%   $117.7528   $117.75   $117.75   $117.80  
  Purchase #4 $56.64   4.358%   $59.1084   $59.11   $59.10   $59.10  
  Purchase #5 $174.54   10.806%   $193.4008   $193.40   $193.40   $193.40  
  Purchase #6 $121.30   3.411%   $125.4375   $125.44   $125.45   $125.40  
  Purchase #7 $193.33   5.580%   $204.1178   $204.12   $204.10   $204.10  
  7 purchase totals = $921.50       $994.6554   $994.66   $994.60   $994.70