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 $174.81   13.622%   $198.6226   $198.62   $198.60   $198.60  
  Purchase #2 $200.90   5.164%   $211.2745   $211.27   $211.25   $211.30  
  Purchase #3 $17.38   12.103%   $19.4835   $19.48   $19.50   $19.50  
  Purchase #4 $107.75   8.721%   $117.1469   $117.15   $117.15   $117.10  
  Purchase #5 $246.26   9.558%   $269.7975   $269.80   $269.80   $269.80  
  Purchase #6 $227.45   7.463%   $244.4246   $244.42   $244.40   $244.40  
  Purchase #7 $56.96   11.522%   $63.5229   $63.52   $63.50   $63.50  
  7 purchase totals = $1,031.51       $1,124.2725   $1,124.26   $1,124.20   $1,124.20