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 $22.60   4.760%   $23.6758   $23.68   $23.70   $23.70  
  Purchase #2 $88.96   4.326%   $92.8084   $92.81   $92.80   $92.80  
  Purchase #3 $118.94   5.488%   $125.4674   $125.47   $125.45   $125.50  
  Purchase #4 $185.64   3.356%   $191.8701   $191.87   $191.85   $191.90  
  Purchase #5 $204.98   9.411%   $224.2707   $224.27   $224.25   $224.30  
  Purchase #6 $233.27   11.611%   $260.355   $260.36   $260.35   $260.40  
  Purchase #7 $215.45   12.321%   $241.9956   $242.00   $242.00   $242.00  
  7 purchase totals = $1,069.84       $1,160.4430   $1,160.46   $1,160.40   $1,160.60