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 $58.37   6.856%   $62.3718   $62.37   $62.35   $62.40  
  Purchase #2 $137.48   13.539%   $156.0934   $156.09   $156.10   $156.10  
  Purchase #3 $233.45   9.426%   $255.455   $255.46   $255.45   $255.50  
  Purchase #4 $245.96   4.797%   $257.7587   $257.76   $257.75   $257.80  
  Purchase #5 $80.30   5.871%   $85.0144   $85.01   $85.00   $85.00  
  Purchase #6 $196.41   9.488%   $215.0454   $215.05   $215.05   $215.00  
  Purchase #7 $213.97   11.836%   $239.2955   $239.30   $239.30   $239.30  
  7 purchase totals = $1,165.94       $1,271.0342   $1,271.04   $1,271.00   $1,271.10