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 $187.35   11.467%   $208.8334   $208.83   $208.85   $208.80  
  Purchase #2 $236.81   11.284%   $263.5316   $263.53   $263.55   $263.50  
  Purchase #3 $233.87   8.617%   $254.0226   $254.02   $254.00   $254.00  
  Purchase #4 $147.76   4.399%   $154.26   $154.26   $154.25   $154.30  
  Purchase #5 $236.69   3.821%   $245.7339   $245.73   $245.75   $245.70  
  Purchase #6 $191.25   10.471%   $211.2758   $211.28   $211.30   $211.30  
  Purchase #7 $117.33   11.550%   $130.8816   $130.88   $130.90   $130.90  
  7 purchase totals = $1,351.06       $1,468.5389   $1,468.53   $1,468.60   $1,468.50