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 $65.26   9.740%   $71.6163   $71.62   $71.60   $71.60  
  Purchase #2 $59.81   7.783%   $64.465   $64.47   $64.45   $64.50  
  Purchase #3 $156.87   8.243%   $169.8008   $169.80   $169.80   $169.80  
  Purchase #4 $49.84   3.534%   $51.6013   $51.60   $51.60   $51.60  
  Purchase #5 $245.69   12.532%   $276.4799   $276.48   $276.50   $276.50  
  Purchase #6 $222.52   9.773%   $244.2669   $244.27   $244.25   $244.30  
  Purchase #7 $138.98   11.795%   $155.3727   $155.37   $155.35   $155.40  
  7 purchase totals = $938.97       $1,033.6029   $1,033.61   $1,033.55   $1,033.70