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 $59.25   4.665%   $62.014   $62.01   $62.00   $62.00  
  Purchase #2 $62.56   10.360%   $69.0412   $69.04   $69.05   $69.00  
  Purchase #3 $27.54   3.179%   $28.4155   $28.42   $28.40   $28.40  
  Purchase #4 $231.94   13.467%   $263.1754   $263.18   $263.20   $263.20  
  Purchase #5 $97.41   3.762%   $101.0746   $101.07   $101.05   $101.10  
  Purchase #6 $205.58   9.533%   $225.1779   $225.18   $225.20   $225.20  
  Purchase #7 $246.53   13.427%   $279.6316   $279.63   $279.65   $279.60  
  7 purchase totals = $930.81       $1,028.5302   $1,028.53   $1,028.55   $1,028.50