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 $176.25   13.497%   $200.0385   $200.04   $200.05   $200.00  
  Purchase #2 $106.65   8.154%   $115.3462   $115.35   $115.35   $115.30  
  Purchase #3 $60.98   8.199%   $65.9798   $65.98   $66.00   $66.00  
  Purchase #4 $44.46   9.493%   $48.6806   $48.68   $48.70   $48.70  
  Purchase #5 $236.47   9.785%   $259.6086   $259.61   $259.60   $259.60  
  Purchase #6 $189.94   3.139%   $195.9022   $195.90   $195.90   $195.90  
  Purchase #7 $8.67   13.126%   $9.808   $9.81   $9.80   $9.80  
  7 purchase totals = $823.42       $895.3639   $895.37   $895.40   $895.30