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 $217.56   9.223%   $237.6256   $237.63   $237.65   $237.60  
  Purchase #2 $122.36   12.506%   $137.6623   $137.66   $137.65   $137.70  
  Purchase #3 $52.41   4.505%   $54.7711   $54.77   $54.75   $54.80  
  Purchase #4 $33.37   8.621%   $36.2468   $36.25   $36.25   $36.20  
  Purchase #5 $245.69   4.805%   $257.4954   $257.50   $257.50   $257.50  
  Purchase #6 $130.46   5.191%   $137.2322   $137.23   $137.25   $137.20  
  Purchase #7 $171.37   13.516%   $194.5324   $194.53   $194.55   $194.50  
  7 purchase totals = $973.22       $1,055.5658   $1,055.57   $1,055.60   $1,055.50