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	$110.85	6.873%	$118.4687	$118.47	$118.45	$118.50
Purchase #2	$89.32	10.194%	$98.4253	$98.43	$98.45	$98.40
Purchase #3	$167.27	13.667%	$190.1308	$190.13	$190.15	$190.10
Purchase #4	$200.26	8.375%	$217.0318	$217.03	$217.05	$217.00
Purchase #5	$62.95	13.247%	$71.289	$71.29	$71.30	$71.30
Purchase #6	$191.74	3.587%	$198.6177	$198.62	$198.60	$198.60
Purchase #7	$245.49	4.853%	$257.4036	$257.40	$257.40	$257.40
7 purchase totals =	$1,067.88		$1,151.3669	$1,151.37	$1,151.40	$1,151.30