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	$156.77	13.346%	$177.6925	$177.69	$177.70	$177.70
Purchase #2	$10.45	13.117%	$11.8207	$11.82	$11.80	$11.80
Purchase #3	$102.84	4.461%	$107.4277	$107.43	$107.45	$107.40
Purchase #4	$82.69	8.681%	$89.8683	$89.87	$89.85	$89.90
Purchase #5	$127.41	7.685%	$137.2015	$137.20	$137.20	$137.20
Purchase #6	$156.69	11.211%	$174.2565	$174.26	$174.25	$174.30
Purchase #7	$174.61	12.506%	$196.4467	$196.45	$196.45	$196.40
7 purchase totals =	$811.46		$894.7139	$894.72	$894.70	$894.70