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 $62.82   6.623%   $66.9806   $66.98   $67.00   $67.00  
  Purchase #2 $164.69   8.102%   $178.0332   $178.03   $178.05   $178.00  
  Purchase #3 $13.34   5.805%   $14.1144   $14.11   $14.10   $14.10  
  Purchase #4 $171.75   13.854%   $195.5442   $195.54   $195.55   $195.50  
  Purchase #5 $125.96   8.352%   $136.4802   $136.48   $136.50   $136.50  
  Purchase #6 $208.94   8.560%   $226.8253   $226.83   $226.85   $226.80  
  Purchase #7 $150.94   11.455%   $168.2302   $168.23   $168.25   $168.20  
  7 purchase totals = $898.44       $986.2081   $986.20   $986.30   $986.10