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 $214.81   12.528%   $241.7214   $241.72   $241.70   $241.70  
  Purchase #2 $224.76   8.775%   $244.4827   $244.48   $244.50   $244.50  
  Purchase #3 $192.83   7.618%   $207.5198   $207.52   $207.50   $207.50  
  Purchase #4 $111.69   4.194%   $116.3743   $116.37   $116.35   $116.40  
  Purchase #5 $47.62   7.625%   $51.251   $51.25   $51.25   $51.30  
  Purchase #6 $152.80   7.271%   $163.9101   $163.91   $163.90   $163.90  
  Purchase #7 $33.87   12.614%   $38.1424   $38.14   $38.15   $38.10  
  7 purchase totals = $978.38       $1,063.4017   $1,063.39   $1,063.35   $1,063.40