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 $58.50   6.307%   $62.1896   $62.19   $62.20   $62.20  
  Purchase #2 $209.59   8.637%   $227.6923   $227.69   $227.70   $227.70  
  Purchase #3 $166.69   12.670%   $187.8096   $187.81   $187.80   $187.80  
  Purchase #4 $89.88   10.541%   $99.3543   $99.35   $99.35   $99.40  
  Purchase #5 $81.44   3.797%   $84.5323   $84.53   $84.55   $84.50  
  Purchase #6 $93.60   13.200%   $105.9552   $105.96   $105.95   $106.00  
  Purchase #7 $7.77   8.188%   $8.4062   $8.41   $8.40   $8.40  
  7 purchase totals = $707.47       $775.9395   $775.94   $775.95   $776.00