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 $106.94   11.433%   $119.1665   $119.17   $119.15   $119.20  
  Purchase #2 $105.63   9.805%   $115.987   $115.99   $116.00   $116.00  
  Purchase #3 $26.37   5.736%   $27.8826   $27.88   $27.90   $27.90  
  Purchase #4 $87.59   6.716%   $93.4725   $93.47   $93.45   $93.50  
  Purchase #5 $76.86   12.278%   $86.2969   $86.30   $86.30   $86.30  
  Purchase #6 $214.41   13.341%   $243.0144   $243.01   $243.00   $243.00  
  Purchase #7 $88.85   5.576%   $93.8043   $93.80   $93.80   $93.80  
  7 purchase totals = $706.65       $779.6242   $779.62   $779.60   $779.70