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 $58.98   5.791%   $62.3955   $62.40   $62.40   $62.40  
  Purchase #2 $117.81   12.557%   $132.6034   $132.60   $132.60   $132.60  
  Purchase #3 $199.39   13.583%   $226.4731   $226.47   $226.45   $226.50  
  Purchase #4 $159.43   5.670%   $168.4697   $168.47   $168.45   $168.50  
  Purchase #5 $236.74   12.467%   $266.2544   $266.25   $266.25   $266.30  
  Purchase #6 $35.32   9.273%   $38.5952   $38.60   $38.60   $38.60  
  Purchase #7 $222.42   6.457%   $236.7817   $236.78   $236.80   $236.80  
  7 purchase totals = $1,030.09       $1,131.5730   $1,131.57   $1,131.55   $1,131.70