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 $66.86   10.845%   $74.111   $74.11   $74.10   $74.10  
  Purchase #2 $234.36   13.546%   $266.1064   $266.11   $266.10   $266.10  
  Purchase #3 $26.38   8.163%   $28.5334   $28.53   $28.55   $28.50  
  Purchase #4 $184.62   7.508%   $198.4813   $198.48   $198.50   $198.50  
  Purchase #5 $145.39   11.682%   $162.3745   $162.37   $162.35   $162.40  
  Purchase #6 $92.72   4.347%   $96.7505   $96.75   $96.75   $96.80  
  Purchase #7 $177.40   3.832%   $184.198   $184.20   $184.20   $184.20  
  7 purchase totals = $927.73       $1,010.5551   $1,010.55   $1,010.55   $1,010.60