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	$99.26	12.653%	$111.8194	$111.82	$111.80	$111.80
Purchase #2	$12.74	11.847%	$14.2493	$14.25	$14.25	$14.20
Purchase #3	$70.85	4.657%	$74.1495	$74.15	$74.15	$74.10
Purchase #4	$57.52	7.578%	$61.8789	$61.88	$61.90	$61.90
Purchase #5	$156.32	6.722%	$166.8278	$166.83	$166.85	$166.80
Purchase #6	$114.81	13.126%	$129.88	$129.88	$129.90	$129.90
Purchase #7	$62.93	7.859%	$67.8757	$67.88	$67.90	$67.90
7 purchase totals =	$574.43		$626.6806	$626.69	$626.75	$626.60