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 $175.87   8.714%   $191.1953   $191.20   $191.20   $191.20  
  Purchase #2 $86.99   11.255%   $96.7807   $96.78   $96.80   $96.80  
  Purchase #3 $228.48   6.839%   $244.1057   $244.11   $244.10   $244.10  
  Purchase #4 $236.39   3.578%   $244.848   $244.85   $244.85   $244.80  
  Purchase #5 $93.65   4.715%   $98.0656   $98.07   $98.05   $98.10  
  Purchase #6 $119.70   6.585%   $127.5822   $127.58   $127.60   $127.60  
  Purchase #7 $10.39   9.422%   $11.3689   $11.37   $11.35   $11.40  
  7 purchase totals = $951.47       $1,013.9464   $1,013.96   $1,013.95   $1,014.00