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 $23.48   5.408%   $24.7498   $24.75   $24.75   $24.70  
  Purchase #2 $250.87   6.381%   $266.878   $266.88   $266.90   $266.90  
  Purchase #3 $203.78   5.518%   $215.0246   $215.02   $215.00   $215.00  
  Purchase #4 $98.80   8.499%   $107.197   $107.20   $107.20   $107.20  
  Purchase #5 $246.83   5.828%   $261.2153   $261.22   $261.20   $261.20  
  Purchase #6 $211.48   10.330%   $233.3259   $233.33   $233.35   $233.30  
  Purchase #7 $243.54   6.452%   $259.2532   $259.25   $259.25   $259.30  
  7 purchase totals = $1,278.78       $1,367.6438   $1,367.65   $1,367.65   $1,367.60