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	$158.81	8.853%	$172.8694	$172.87	$172.85	$172.90
Purchase #2	$203.32	12.267%	$228.2613	$228.26	$228.25	$228.30
Purchase #3	$153.26	9.146%	$167.2772	$167.28	$167.30	$167.30
Purchase #4	$73.44	13.283%	$83.195	$83.20	$83.20	$83.20
Purchase #5	$32.42	4.819%	$33.9823	$33.98	$34.00	$34.00
Purchase #6	$65.51	8.152%	$70.8504	$70.85	$70.85	$70.90
Purchase #7	$168.80	10.462%	$186.4599	$186.46	$186.45	$186.50
7 purchase totals =	$855.56		$942.8955	$942.90	$942.90	$943.10