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	$86.72	4.725%	$90.8175	$90.82	$90.80	$90.80
Purchase #2	$50.55	5.121%	$53.1387	$53.14	$53.15	$53.10
Purchase #3	$188.89	11.593%	$210.788	$210.79	$210.80	$210.80
Purchase #4	$12.93	8.860%	$14.0756	$14.08	$14.10	$14.10
Purchase #5	$60.91	8.519%	$66.0989	$66.10	$66.10	$66.10
Purchase #6	$97.78	13.866%	$111.3382	$111.34	$111.35	$111.30
Purchase #7	$209.65	3.592%	$217.1806	$217.18	$217.20	$217.20
7 purchase totals =	$707.43		$763.4375	$763.45	$763.50	$763.40