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	$36.88	3.716%	$38.2505	$38.25	$38.25	$38.30
Purchase #2	$127.40	5.321%	$134.179	$134.18	$134.20	$134.20
Purchase #3	$235.93	7.446%	$253.4973	$253.50	$253.50	$253.50
Purchase #4	$59.83	4.658%	$62.6169	$62.62	$62.60	$62.60
Purchase #5	$160.41	7.704%	$172.768	$172.77	$172.75	$172.80
Purchase #6	$89.32	10.367%	$98.5798	$98.58	$98.60	$98.60
Purchase #7	$247.93	10.308%	$273.4866	$273.49	$273.50	$273.50
7 purchase totals =	$957.70		$1,033.3781	$1,033.39	$1,033.40	$1,033.50