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 $111.62   3.270%   $115.27   $115.27   $115.25   $115.30  
  Purchase #2 $186.27   3.477%   $192.7466   $192.75   $192.75   $192.70  
  Purchase #3 $233.41   13.433%   $264.764   $264.76   $264.75   $264.80  
  Purchase #4 $127.73   4.352%   $133.2888   $133.29   $133.30   $133.30  
  Purchase #5 $195.70   5.613%   $206.6846   $206.68   $206.70   $206.70  
  Purchase #6 $170.25   3.668%   $176.4948   $176.49   $176.50   $176.50  
  Purchase #7 $137.77   13.377%   $156.1995   $156.20   $156.20   $156.20  
  7 purchase totals = $1,162.75       $1,245.4483   $1,245.44   $1,245.45   $1,245.50