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	$92.59	9.389%	$101.2833	$101.28	$101.30	$101.30
Purchase #2	$151.72	9.614%	$166.3064	$166.31	$166.30	$166.30
Purchase #3	$6.33	11.392%	$7.0511	$7.05	$7.05	$7.10
Purchase #4	$184.47	3.352%	$190.6534	$190.65	$190.65	$190.70
Purchase #5	$42.59	13.274%	$48.2434	$48.24	$48.25	$48.20
Purchase #6	$143.69	5.422%	$151.4809	$151.48	$151.50	$151.50
Purchase #7	$132.53	4.414%	$138.3799	$138.38	$138.40	$138.40
7 purchase totals =	$753.92		$803.3984	$803.39	$803.45	$803.50