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 $53.29   3.138%   $54.9622   $54.96   $54.95   $55.00  
  Purchase #2 $72.65   6.333%   $77.2509   $77.25   $77.25   $77.30  
  Purchase #3 $194.92   6.608%   $207.8003   $207.80   $207.80   $207.80  
  Purchase #4 $110.73   13.715%   $125.9166   $125.92   $125.90   $125.90  
  Purchase #5 $203.60   5.787%   $215.3823   $215.38   $215.40   $215.40  
  Purchase #6 $225.63   8.565%   $244.9552   $244.96   $244.95   $245.00  
  Purchase #7 $186.73   3.570%   $193.3963   $193.40   $193.40   $193.40  
  7 purchase totals = $1,047.55       $1,119.6638   $1,119.67   $1,119.65   $1,119.80