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	$34.39	8.739%	$37.3953	$37.40	$37.40	$37.40
Purchase #2	$30.68	9.152%	$33.4878	$33.49	$33.50	$33.50
Purchase #3	$73.99	5.143%	$77.7953	$77.80	$77.80	$77.80
Purchase #4	$89.61	10.567%	$99.0791	$99.08	$99.10	$99.10
Purchase #5	$199.87	11.507%	$222.869	$222.87	$222.85	$222.90
Purchase #6	$182.88	5.222%	$192.43	$192.43	$192.45	$192.40
Purchase #7	$47.35	5.572%	$49.9883	$49.99	$50.00	$50.00
7 purchase totals =	$658.77		$713.0448	$713.06	$713.10	$713.10