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 $86.87   6.196%   $92.2525   $92.25   $92.25   $92.30  
  Purchase #2 $85.76   11.589%   $95.6987   $95.70   $95.70   $95.70  
  Purchase #3 $59.79   10.202%   $65.8898   $65.89   $65.90   $65.90  
  Purchase #4 $147.72   3.430%   $152.7868   $152.79   $152.80   $152.80  
  Purchase #5 $214.44   5.672%   $226.603   $226.60   $226.60   $226.60  
  Purchase #6 $119.54   5.147%   $125.6927   $125.69   $125.70   $125.70  
  Purchase #7 $224.29   9.535%   $245.6761   $245.68   $245.70   $245.70  
  7 purchase totals = $938.41       $1,004.5996   $1,004.60   $1,004.65   $1,004.70