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	$115.27	10.516%	$127.3918	$127.39	$127.40	$127.40
Purchase #2	$145.70	5.118%	$153.1569	$153.16	$153.15	$153.20
Purchase #3	$215.75	8.144%	$233.3207	$233.32	$233.30	$233.30
Purchase #4	$249.60	5.381%	$263.031	$263.03	$263.05	$263.00
Purchase #5	$42.49	13.768%	$48.34	$48.34	$48.35	$48.30
Purchase #6	$95.75	7.677%	$103.1007	$103.10	$103.10	$103.10
Purchase #7	$99.99	13.275%	$113.2637	$113.26	$113.25	$113.30
7 purchase totals =	$964.55		$1,041.6048	$1,041.60	$1,041.60	$1,041.60