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	$221.97	5.306%	$233.7477	$233.75	$233.75	$233.70
Purchase #2	$160.48	7.782%	$172.9686	$172.97	$172.95	$173.00
Purchase #3	$71.37	8.624%	$77.5249	$77.52	$77.50	$77.50
Purchase #4	$165.81	6.427%	$176.4666	$176.47	$176.45	$176.50
Purchase #5	$87.28	3.185%	$90.0599	$90.06	$90.05	$90.10
Purchase #6	$69.42	13.605%	$78.8646	$78.86	$78.85	$78.90
Purchase #7	$67.46	5.447%	$71.1345	$71.13	$71.15	$71.10
7 purchase totals =	$843.79		$900.7668	$900.76	$900.70	$900.80