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 $149.47   8.578%   $162.2915   $162.29   $162.30   $162.30  
  Purchase #2 $250.87   13.183%   $283.9422   $283.94   $283.95   $283.90  
  Purchase #3 $125.93   8.193%   $136.2474   $136.25   $136.25   $136.20  
  Purchase #4 $154.90   4.181%   $161.3764   $161.38   $161.40   $161.40  
  Purchase #5 $64.70   8.824%   $70.4091   $70.41   $70.40   $70.40  
  Purchase #6 $177.26   3.662%   $183.7513   $183.75   $183.75   $183.80  
  Purchase #7 $60.31   6.672%   $64.3339   $64.33   $64.35   $64.30  
  7 purchase totals = $983.44       $1,062.3518   $1,062.35   $1,062.40   $1,062.30