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 $185.38   4.789%   $194.2578   $194.26   $194.25   $194.30  
  Purchase #2 $62.50   13.595%   $70.9969   $71.00   $71.00   $71.00  
  Purchase #3 $228.41   8.314%   $247.4   $247.40   $247.40   $247.40  
  Purchase #4 $86.99   13.550%   $98.7771   $98.78   $98.80   $98.80  
  Purchase #5 $7.86   10.475%   $8.6833   $8.68   $8.70   $8.70  
  Purchase #6 $201.69   3.743%   $209.2393   $209.24   $209.25   $209.20  
  Purchase #7 $176.46   6.187%   $187.3776   $187.38   $187.40   $187.40  
  7 purchase totals = $949.29       $1,016.7320   $1,016.74   $1,016.80   $1,016.80