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 $56.45   10.493%   $62.3733   $62.37   $62.35   $62.40  
  Purchase #2 $94.39   11.659%   $105.3949   $105.39   $105.40   $105.40  
  Purchase #3 $174.40   10.275%   $192.3196   $192.32   $192.30   $192.30  
  Purchase #4 $233.75   8.235%   $252.9993   $253.00   $253.00   $253.00  
  Purchase #5 $154.48   12.430%   $173.6819   $173.68   $173.70   $173.70  
  Purchase #6 $157.59   9.453%   $172.487   $172.49   $172.50   $172.50  
  Purchase #7 $226.42   7.242%   $242.8173   $242.82   $242.80   $242.80  
  7 purchase totals = $1,097.48       $1,202.0733   $1,202.07   $1,202.05   $1,202.10