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 $156.73   3.395%   $162.051   $162.05   $162.05   $162.10  
  Purchase #2 $85.83   11.311%   $95.5382   $95.54   $95.55   $95.50  
  Purchase #3 $178.25   3.459%   $184.4157   $184.42   $184.40   $184.40  
  Purchase #4 $90.73   6.638%   $96.7527   $96.75   $96.75   $96.80  
  Purchase #5 $84.59   10.841%   $93.7604   $93.76   $93.75   $93.80  
  Purchase #6 $157.72   11.448%   $175.7758   $175.78   $175.80   $175.80  
  Purchase #7 $195.42   10.169%   $215.2923   $215.29   $215.30   $215.30  
  7 purchase totals = $949.27       $1,023.5861   $1,023.59   $1,023.60   $1,023.70