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 $216.72   6.715%   $231.2727   $231.27   $231.25   $231.30  
  Purchase #2 $117.88   5.379%   $124.2208   $124.22   $124.20   $124.20  
  Purchase #3 $222.85   9.812%   $244.716   $244.72   $244.70   $244.70  
  Purchase #4 $206.61   6.462%   $219.9611   $219.96   $219.95   $220.00  
  Purchase #5 $208.76   13.215%   $236.3476   $236.35   $236.35   $236.30  
  Purchase #6 $131.30   6.722%   $140.126   $140.13   $140.15   $140.10  
  Purchase #7 $248.26   6.381%   $264.1015   $264.10   $264.10   $264.10  
  7 purchase totals = $1,352.38       $1,460.7457   $1,460.75   $1,460.70   $1,460.70