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	$60.88	5.373%	$64.1511	$64.15	$64.15	$64.20
Purchase #2	$61.40	6.450%	$65.3603	$65.36	$65.35	$65.40
Purchase #3	$93.73	6.464%	$99.7887	$99.79	$99.80	$99.80
Purchase #4	$48.28	4.795%	$50.595	$50.60	$50.60	$50.60
Purchase #5	$16.73	12.560%	$18.8313	$18.83	$18.85	$18.80
Purchase #6	$162.82	7.870%	$175.6339	$175.63	$175.65	$175.60
Purchase #7	$113.72	3.557%	$117.765	$117.77	$117.75	$117.80
7 purchase totals =	$557.56		$592.1253	$592.13	$592.15	$592.20