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	$218.94	4.333%	$228.4267	$228.43	$228.45	$228.40
Purchase #2	$167.89	7.369%	$180.2618	$180.26	$180.25	$180.30
Purchase #3	$122.43	4.332%	$127.7337	$127.73	$127.75	$127.70
Purchase #4	$60.54	6.572%	$64.5187	$64.52	$64.50	$64.50
Purchase #5	$15.92	11.666%	$17.7772	$17.78	$17.80	$17.80
Purchase #6	$48.83	8.680%	$53.0684	$53.07	$53.05	$53.10
Purchase #7	$112.27	11.737%	$125.4471	$125.45	$125.45	$125.40
7 purchase totals =	$746.82		$797.2336	$797.24	$797.25	$797.20