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	$152.90	8.349%	$165.6656	$165.67	$165.65	$165.70
Purchase #2	$173.27	7.206%	$185.7558	$185.76	$185.75	$185.80
Purchase #3	$99.33	10.333%	$109.5938	$109.59	$109.60	$109.60
Purchase #4	$114.42	11.467%	$127.5405	$127.54	$127.55	$127.50
Purchase #5	$10.66	8.548%	$11.5712	$11.57	$11.55	$11.60
Purchase #6	$113.66	4.147%	$118.3735	$118.37	$118.35	$118.40
Purchase #7	$61.28	5.246%	$64.4947	$64.49	$64.50	$64.50
7 purchase totals =	$725.52		$782.9951	$782.99	$782.95	$783.10