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 $241.66   10.479%   $266.9836   $266.98   $267.00   $267.00  
  Purchase #2 $67.89   10.578%   $75.0714   $75.07   $75.05   $75.10  
  Purchase #3 $221.34   3.556%   $229.2109   $229.21   $229.20   $229.20  
  Purchase #4 $209.66   11.185%   $233.1105   $233.11   $233.10   $233.10  
  Purchase #5 $188.60   10.473%   $208.3521   $208.35   $208.35   $208.40  
  Purchase #6 $218.88   7.245%   $234.7379   $234.74   $234.75   $234.70  
  Purchase #7 $201.91   12.243%   $226.6298   $226.63   $226.65   $226.60  
  7 purchase totals = $1,349.94       $1,474.0962   $1,474.09   $1,474.10   $1,474.10