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 $215.62   7.623%   $232.0567   $232.06   $232.05   $232.10  
  Purchase #2 $185.74   6.713%   $198.2087   $198.21   $198.20   $198.20  
  Purchase #3 $13.35   5.396%   $14.0704   $14.07   $14.05   $14.10  
  Purchase #4 $161.77   3.271%   $167.0615   $167.06   $167.05   $167.10  
  Purchase #5 $150.62   5.338%   $158.6601   $158.66   $158.65   $158.70  
  Purchase #6 $84.75   4.387%   $88.468   $88.47   $88.45   $88.50  
  Purchase #7 $34.67   7.647%   $37.3212   $37.32   $37.30   $37.30  
  7 purchase totals = $846.52       $895.8466   $895.85   $895.75   $896.00