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 $119.25   3.684%   $123.6432   $123.64   $123.65   $123.60  
  Purchase #2 $185.98   11.330%   $207.0515   $207.05   $207.05   $207.10  
  Purchase #3 $196.59   6.752%   $209.8638   $209.86   $209.85   $209.90  
  Purchase #4 $163.94   7.728%   $176.6093   $176.61   $176.60   $176.60  
  Purchase #5 $243.55   5.679%   $257.3812   $257.38   $257.40   $257.40  
  Purchase #6 $8.69   9.339%   $9.5016   $9.50   $9.50   $9.50  
  Purchase #7 $151.82   5.752%   $160.5527   $160.55   $160.55   $160.60  
  7 purchase totals = $1,069.82       $1,144.6033   $1,144.59   $1,144.60   $1,144.70