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 $118.41   4.455%   $123.6852   $123.69   $123.70   $123.70  
  Purchase #2 $215.44   12.271%   $241.8766   $241.88   $241.90   $241.90  
  Purchase #3 $201.72   11.422%   $224.7605   $224.76   $224.75   $224.80  
  Purchase #4 $245.62   4.706%   $257.1789   $257.18   $257.20   $257.20  
  Purchase #5 $77.74   5.141%   $81.7366   $81.74   $81.75   $81.70  
  Purchase #6 $53.76   8.561%   $58.3624   $58.36   $58.35   $58.40  
  Purchase #7 $113.79   11.799%   $127.2161   $127.22   $127.20   $127.20  
  7 purchase totals = $1,026.48       $1,114.8163   $1,114.83   $1,114.85   $1,114.90