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 $50.95   4.582%   $53.2845   $53.28   $53.30   $53.30  
  Purchase #2 $239.87   13.757%   $272.8689   $272.87   $272.85   $272.90  
  Purchase #3 $226.76   12.260%   $254.5608   $254.56   $254.55   $254.60  
  Purchase #4 $159.94   13.110%   $180.9081   $180.91   $180.90   $180.90  
  Purchase #5 $163.34   6.198%   $173.4638   $173.46   $173.45   $173.50  
  Purchase #6 $60.49   8.503%   $65.6335   $65.63   $65.65   $65.60  
  Purchase #7 $184.57   5.737%   $195.1588   $195.16   $195.15   $195.20  
  7 purchase totals = $1,085.92       $1,195.8784   $1,195.87   $1,195.85   $1,196.00