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 $233.33   5.672%   $246.5645   $246.56   $246.55   $246.60  
  Purchase #2 $214.71   5.401%   $226.3065   $226.31   $226.30   $226.30  
  Purchase #3 $80.62   3.478%   $83.424   $83.42   $83.40   $83.40  
  Purchase #4 $200.54   8.318%   $217.2209   $217.22   $217.20   $217.20  
  Purchase #5 $19.96   10.479%   $22.0516   $22.05   $22.05   $22.10  
  Purchase #6 $74.34   3.113%   $76.6542   $76.65   $76.65   $76.70  
  Purchase #7 $168.25   13.366%   $190.7383   $190.74   $190.75   $190.70  
  7 purchase totals = $991.75       $1,062.9600   $1,062.95   $1,062.90   $1,063.00