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 $116.50   9.637%   $127.7271   $127.73   $127.75   $127.70  
  Purchase #2 $191.48   11.425%   $213.3566   $213.36   $213.35   $213.40  
  Purchase #3 $200.93   12.817%   $226.6832   $226.68   $226.70   $226.70  
  Purchase #4 $82.54   4.763%   $86.4714   $86.47   $86.45   $86.50  
  Purchase #5 $134.90   9.286%   $147.4268   $147.43   $147.45   $147.40  
  Purchase #6 $213.50   11.215%   $237.444   $237.44   $237.45   $237.40  
  Purchase #7 $19.71   10.336%   $21.7472   $21.75   $21.75   $21.70  
  7 purchase totals = $959.56       $1,060.8563   $1,060.86   $1,060.90   $1,060.80