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 $34.43   3.670%   $35.6936   $35.69   $35.70   $35.70  
  Purchase #2 $199.74   4.182%   $208.0931   $208.09   $208.10   $208.10  
  Purchase #3 $163.51   6.221%   $173.682   $173.68   $173.70   $173.70  
  Purchase #4 $216.97   5.278%   $228.4217   $228.42   $228.40   $228.40  
  Purchase #5 $10.91   3.216%   $11.2609   $11.26   $11.25   $11.30  
  Purchase #6 $133.57   9.823%   $146.6906   $146.69   $146.70   $146.70  
  Purchase #7 $176.84   8.644%   $192.126   $192.13   $192.15   $192.10  
  7 purchase totals = $935.97       $995.9679   $995.96   $996.00   $996.00