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 $169.86   7.502%   $182.6029   $182.60   $182.60   $182.60  
  Purchase #2 $237.52   13.497%   $269.5781   $269.58   $269.60   $269.60  
  Purchase #3 $152.50   5.861%   $161.438   $161.44   $161.45   $161.40  
  Purchase #4 $48.78   6.184%   $51.7966   $51.80   $51.80   $51.80  
  Purchase #5 $216.47   4.560%   $226.341   $226.34   $226.35   $226.30  
  Purchase #6 $209.87   10.578%   $232.07   $232.07   $232.05   $232.10  
  Purchase #7 $157.72   12.822%   $177.9429   $177.94   $177.95   $177.90  
  7 purchase totals = $1,192.72       $1,301.7695   $1,301.77   $1,301.80   $1,301.70