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 $203.81   5.445%   $214.9075   $214.91   $214.90   $214.90  
  Purchase #2 $37.66   4.630%   $39.4037   $39.40   $39.40   $39.40  
  Purchase #3 $212.27   10.147%   $233.809   $233.81   $233.80   $233.80  
  Purchase #4 $119.85   7.801%   $129.1995   $129.20   $129.20   $129.20  
  Purchase #5 $75.47   9.318%   $82.5023   $82.50   $82.50   $82.50  
  Purchase #6 $96.78   13.786%   $110.1221   $110.12   $110.10   $110.10  
  Purchase #7 $191.85   11.800%   $214.4883   $214.49   $214.50   $214.50  
  7 purchase totals = $937.69       $1,024.4324   $1,024.43   $1,024.40   $1,024.40