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	$80.95	10.315%	$89.3	$89.30	$89.30	$89.30
Purchase #2	$156.86	10.676%	$173.6064	$173.61	$173.60	$173.60
Purchase #3	$247.45	3.235%	$255.455	$255.46	$255.45	$255.50
Purchase #4	$223.43	8.397%	$242.1914	$242.19	$242.20	$242.20
Purchase #5	$49.66	7.575%	$53.4217	$53.42	$53.40	$53.40
Purchase #6	$58.30	12.527%	$65.6032	$65.60	$65.60	$65.60
Purchase #7	$228.27	6.293%	$242.635	$242.64	$242.65	$242.60
7 purchase totals =	$1,044.92		$1,122.2127	$1,122.22	$1,122.20	$1,122.20