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	$111.71	5.356%	$117.6932	$117.69	$117.70	$117.70
Purchase #2	$12.26	9.756%	$13.4561	$13.46	$13.45	$13.50
Purchase #3	$182.49	4.210%	$190.1728	$190.17	$190.15	$190.20
Purchase #4	$123.45	8.109%	$133.4606	$133.46	$133.45	$133.50
Purchase #5	$49.91	5.103%	$52.4569	$52.46	$52.45	$52.50
Purchase #6	$92.50	7.107%	$99.074	$99.07	$99.05	$99.10
Purchase #7	$99.52	7.831%	$107.3134	$107.31	$107.30	$107.30
7 purchase totals =	$671.84		$713.6270	$713.62	$713.55	$713.80