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 $61.59   13.499%   $69.904   $69.90   $69.90   $69.90  
  Purchase #2 $119.66   5.835%   $126.6422   $126.64   $126.65   $126.60  
  Purchase #3 $226.92   5.532%   $239.4732   $239.47   $239.45   $239.50  
  Purchase #4 $239.27   4.486%   $250.0037   $250.00   $250.00   $250.00  
  Purchase #5 $156.70   9.821%   $172.0895   $172.09   $172.10   $172.10  
  Purchase #6 $100.62   3.703%   $104.346   $104.35   $104.35   $104.30  
  Purchase #7 $109.66   3.669%   $113.6834   $113.68   $113.70   $113.70  
  7 purchase totals = $1,014.42       $1,076.1420   $1,076.13   $1,076.15   $1,076.10