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 $54.35   11.648%   $60.6807   $60.68   $60.70   $60.70  
  Purchase #2 $83.30   4.678%   $87.1968   $87.20   $87.20   $87.20  
  Purchase #3 $185.52   12.434%   $208.5876   $208.59   $208.60   $208.60  
  Purchase #4 $56.48   12.233%   $63.3892   $63.39   $63.40   $63.40  
  Purchase #5 $214.62   5.617%   $226.6752   $226.68   $226.70   $226.70  
  Purchase #6 $77.96   5.192%   $82.0077   $82.01   $82.00   $82.00  
  Purchase #7 $6.63   11.304%   $7.3795   $7.38   $7.40   $7.40  
  7 purchase totals = $678.86       $735.9167   $735.93   $736.00   $736.00