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	$225.29	3.805%	$233.8623	$233.86	$233.85	$233.90
Purchase #2	$145.45	3.171%	$150.0622	$150.06	$150.05	$150.10
Purchase #3	$83.28	12.698%	$93.8549	$93.85	$93.85	$93.90
Purchase #4	$207.45	6.171%	$220.2517	$220.25	$220.25	$220.30
Purchase #5	$146.83	4.752%	$153.8074	$153.81	$153.80	$153.80
Purchase #6	$188.99	3.748%	$196.0733	$196.07	$196.05	$196.10
Purchase #7	$99.66	12.218%	$111.8365	$111.84	$111.85	$111.80
7 purchase totals =	$1,096.95		$1,159.7483	$1,159.74	$1,159.70	$1,159.90