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 $95.39   8.614%   $103.6069   $103.61   $103.60   $103.60  
  Purchase #2 $114.99   8.237%   $124.4617   $124.46   $124.45   $124.50  
  Purchase #3 $69.38   3.722%   $71.9623   $71.96   $71.95   $72.00  
  Purchase #4 $210.53   11.547%   $234.8399   $234.84   $234.85   $234.80  
  Purchase #5 $185.80   8.396%   $201.3998   $201.40   $201.40   $201.40  
  Purchase #6 $215.59   5.609%   $227.6824   $227.68   $227.70   $227.70  
  Purchase #7 $205.47   5.477%   $216.7236   $216.72   $216.70   $216.70  
  7 purchase totals = $1,097.15       $1,180.6766   $1,180.67   $1,180.65   $1,180.70