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 $56.94   9.401%   $62.2929   $62.29   $62.30   $62.30  
  Purchase #2 $65.81   4.104%   $68.5108   $68.51   $68.50   $68.50  
  Purchase #3 $14.69   4.283%   $15.3192   $15.32   $15.30   $15.30  
  Purchase #4 $46.98   11.860%   $52.5518   $52.55   $52.55   $52.60  
  Purchase #5 $193.68   10.716%   $214.4347   $214.43   $214.45   $214.40  
  Purchase #6 $236.37   3.269%   $244.0969   $244.10   $244.10   $244.10  
  Purchase #7 $187.56   9.588%   $205.5433   $205.54   $205.55   $205.50  
  7 purchase totals = $802.03       $862.7496   $862.74   $862.75   $862.70