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 $116.25   8.542%   $126.1801   $126.18   $126.20   $126.20  
  Purchase #2 $61.58   12.492%   $69.2726   $69.27   $69.25   $69.30  
  Purchase #3 $125.64   8.806%   $136.7039   $136.70   $136.70   $136.70  
  Purchase #4 $31.91   8.749%   $34.7018   $34.70   $34.70   $34.70  
  Purchase #5 $81.71   5.554%   $86.2482   $86.25   $86.25   $86.20  
  Purchase #6 $231.74   8.831%   $252.205   $252.21   $252.20   $252.20  
  Purchase #7 $223.90   10.642%   $247.7274   $247.73   $247.75   $247.70  
  7 purchase totals = $872.73       $953.0390   $953.04   $953.05   $953.00