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 $116.38   5.575%   $122.8682   $122.87   $122.85   $122.90  
  Purchase #2 $43.33   6.376%   $46.0927   $46.09   $46.10   $46.10  
  Purchase #3 $83.46   3.393%   $86.2918   $86.29   $86.30   $86.30  
  Purchase #4 $171.69   6.749%   $183.2774   $183.28   $183.30   $183.30  
  Purchase #5 $177.64   4.399%   $185.4544   $185.45   $185.45   $185.50  
  Purchase #6 $13.30   3.263%   $13.734   $13.73   $13.75   $13.70  
  Purchase #7 $60.89   4.443%   $63.5953   $63.60   $63.60   $63.60  
  7 purchase totals = $666.69       $701.3138   $701.31   $701.35   $701.40