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 $112.50   11.624%   $125.577   $125.58   $125.60   $125.60  
  Purchase #2 $231.36   8.312%   $250.5906   $250.59   $250.60   $250.60  
  Purchase #3 $220.55   7.580%   $237.2677   $237.27   $237.25   $237.30  
  Purchase #4 $80.26   7.554%   $86.3228   $86.32   $86.30   $86.30  
  Purchase #5 $144.56   11.618%   $161.355   $161.36   $161.35   $161.40  
  Purchase #6 $181.75   5.719%   $192.1443   $192.14   $192.15   $192.10  
  Purchase #7 $9.50   4.233%   $9.9021   $9.90   $9.90   $9.90  
  7 purchase totals = $980.48       $1,063.1595   $1,063.16   $1,063.15   $1,063.20