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 $67.73   3.150%   $69.8635   $69.86   $69.85   $69.90  
  Purchase #2 $19.93   10.374%   $21.9975   $22.00   $22.00   $22.00  
  Purchase #3 $100.32   5.496%   $105.8336   $105.83   $105.85   $105.80  
  Purchase #4 $249.37   7.342%   $267.6787   $267.68   $267.70   $267.70  
  Purchase #5 $156.90   4.335%   $163.7016   $163.70   $163.70   $163.70  
  Purchase #6 $184.70   3.155%   $190.5273   $190.53   $190.55   $190.50  
  Purchase #7 $132.89   7.307%   $142.6003   $142.60   $142.60   $142.60  
  7 purchase totals = $911.84       $962.2025   $962.20   $962.25   $962.20