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 $85.68   9.360%   $93.6996   $93.70   $93.70   $93.70  
  Purchase #2 $112.90   3.228%   $116.5444   $116.54   $116.55   $116.50  
  Purchase #3 $144.59   13.475%   $164.0735   $164.07   $164.05   $164.10  
  Purchase #4 $169.86   10.426%   $187.5696   $187.57   $187.55   $187.60  
  Purchase #5 $50.33   12.536%   $56.6394   $56.64   $56.65   $56.60  
  Purchase #6 $246.30   13.204%   $278.8215   $278.82   $278.80   $278.80  
  Purchase #7 $53.44   8.820%   $58.1534   $58.15   $58.15   $58.20  
  7 purchase totals = $863.10       $955.5014   $955.49   $955.45   $955.50