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	$105.41	5.582%	$111.294	$111.29	$111.30	$111.30
Purchase #2	$118.82	6.559%	$126.6134	$126.61	$126.60	$126.60
Purchase #3	$233.52	12.347%	$262.3527	$262.35	$262.35	$262.40
Purchase #4	$44.41	6.780%	$47.421	$47.42	$47.40	$47.40
Purchase #5	$172.49	13.710%	$196.1384	$196.14	$196.15	$196.10
Purchase #6	$94.63	13.685%	$107.5801	$107.58	$107.60	$107.60
Purchase #7	$46.54	8.331%	$50.4172	$50.42	$50.40	$50.40
7 purchase totals =	$815.82		$901.8168	$901.81	$901.80	$901.80