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 $162.80   12.195%   $182.6535   $182.65   $182.65   $182.70  
  Purchase #2 $195.42   9.530%   $214.0435   $214.04   $214.05   $214.00  
  Purchase #3 $32.50   5.678%   $34.3454   $34.35   $34.35   $34.30  
  Purchase #4 $93.93   5.296%   $98.9045   $98.90   $98.90   $98.90  
  Purchase #5 $249.36   5.191%   $262.3043   $262.30   $262.30   $262.30  
  Purchase #6 $245.50   11.481%   $273.6859   $273.69   $273.70   $273.70  
  Purchase #7 $95.28   7.797%   $102.709   $102.71   $102.70   $102.70  
  7 purchase totals = $1,074.79       $1,168.6461   $1,168.64   $1,168.65   $1,168.60