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 $246.56   6.304%   $262.1031   $262.10   $262.10   $262.10  
  Purchase #2 $144.87   8.810%   $157.633   $157.63   $157.65   $157.60  
  Purchase #3 $92.97   6.870%   $99.357   $99.36   $99.35   $99.40  
  Purchase #4 $194.93   13.682%   $221.6003   $221.60   $221.60   $221.60  
  Purchase #5 $232.46   7.837%   $250.6779   $250.68   $250.70   $250.70  
  Purchase #6 $135.91   13.802%   $154.6683   $154.67   $154.65   $154.70  
  Purchase #7 $86.52   9.807%   $95.005   $95.01   $95.00   $95.00  
  7 purchase totals = $1,134.22       $1,241.0446   $1,241.05   $1,241.05   $1,241.10