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 $33.61   6.730%   $35.872   $35.87   $35.85   $35.90  
  Purchase #2 $226.99   13.798%   $258.3101   $258.31   $258.30   $258.30  
  Purchase #3 $122.91   13.302%   $139.2595   $139.26   $139.25   $139.30  
  Purchase #4 $179.35   4.594%   $187.5893   $187.59   $187.60   $187.60  
  Purchase #5 $60.94   7.559%   $65.5465   $65.55   $65.55   $65.50  
  Purchase #6 $127.29   4.382%   $132.8678   $132.87   $132.85   $132.90  
  Purchase #7 $69.28   7.865%   $74.7289   $74.73   $74.75   $74.70  
  7 purchase totals = $820.37       $894.1741   $894.18   $894.15   $894.20