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 $33.67   4.513%   $35.1895   $35.19   $35.20   $35.20  
  Purchase #2 $162.76   7.723%   $175.33   $175.33   $175.35   $175.30  
  Purchase #3 $220.42   11.243%   $245.2018   $245.20   $245.20   $245.20  
  Purchase #4 $80.69   9.775%   $88.5774   $88.58   $88.60   $88.60  
  Purchase #5 $95.34   5.177%   $100.2758   $100.28   $100.30   $100.30  
  Purchase #6 $49.27   13.836%   $56.087   $56.09   $56.10   $56.10  
  Purchase #7 $177.49   5.627%   $187.4774   $187.48   $187.50   $187.50  
  7 purchase totals = $819.64       $888.1389   $888.15   $888.25   $888.20