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 $60.68   3.413%   $62.751   $62.75   $62.75   $62.80  
  Purchase #2 $52.38   13.848%   $59.6336   $59.63   $59.65   $59.60  
  Purchase #3 $129.48   9.220%   $141.4181   $141.42   $141.40   $141.40  
  Purchase #4 $146.37   9.794%   $160.7055   $160.71   $160.70   $160.70  
  Purchase #5 $207.68   5.123%   $218.3194   $218.32   $218.30   $218.30  
  Purchase #6 $75.81   8.153%   $81.9908   $81.99   $82.00   $82.00  
  Purchase #7 $192.65   12.431%   $216.5983   $216.60   $216.60   $216.60  
  7 purchase totals = $865.05       $941.4167   $941.42   $941.40   $941.40