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	$111.68	10.300%	$123.183	$123.18	$123.20	$123.20
Purchase #2	$188.68	10.520%	$208.5291	$208.53	$208.55	$208.50
Purchase #3	$20.46	6.193%	$21.7271	$21.73	$21.75	$21.70
Purchase #4	$79.67	13.491%	$90.4183	$90.42	$90.40	$90.40
Purchase #5	$180.28	3.780%	$187.0946	$187.09	$187.10	$187.10
Purchase #6	$76.71	13.203%	$86.838	$86.84	$86.85	$86.80
Purchase #7	$35.37	6.610%	$37.708	$37.71	$37.70	$37.70
7 purchase totals =	$692.85		$755.4981	$755.50	$755.55	$755.40