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 $194.50   8.795%   $211.6063   $211.61   $211.60   $211.60  
  Purchase #2 $26.74   5.314%   $28.161   $28.16   $28.15   $28.20  
  Purchase #3 $35.57   4.621%   $37.2137   $37.21   $37.20   $37.20  
  Purchase #4 $70.90   7.231%   $76.0268   $76.03   $76.05   $76.00  
  Purchase #5 $20.90   4.475%   $21.8353   $21.84   $21.85   $21.80  
  Purchase #6 $123.83   5.141%   $130.1961   $130.20   $130.20   $130.20  
  Purchase #7 $223.35   10.671%   $247.1837   $247.18   $247.20   $247.20  
  7 purchase totals = $695.79       $752.2229   $752.23   $752.25   $752.20