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	$107.92	5.757%	$114.133	$114.13	$114.15	$114.10
Purchase #2	$114.27	11.767%	$127.7162	$127.72	$127.70	$127.70
Purchase #3	$82.26	8.859%	$89.5474	$89.55	$89.55	$89.50
Purchase #4	$144.60	5.689%	$152.8263	$152.83	$152.85	$152.80
Purchase #5	$162.87	10.369%	$179.758	$179.76	$179.75	$179.80
Purchase #6	$91.96	3.590%	$95.2614	$95.26	$95.25	$95.30
Purchase #7	$58.29	5.317%	$61.3893	$61.39	$61.40	$61.40
7 purchase totals =	$762.17		$820.6316	$820.64	$820.65	$820.60