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	$30.37	8.476%	$32.9442	$32.94	$32.95	$32.90
Purchase #2	$56.95	5.104%	$59.8567	$59.86	$59.85	$59.90
Purchase #3	$87.74	13.434%	$99.527	$99.53	$99.55	$99.50
Purchase #4	$114.91	10.782%	$127.2996	$127.30	$127.30	$127.30
Purchase #5	$217.87	12.288%	$244.6419	$244.64	$244.65	$244.60
Purchase #6	$120.63	5.371%	$127.109	$127.11	$127.10	$127.10
Purchase #7	$62.56	13.318%	$70.8917	$70.89	$70.90	$70.90
7 purchase totals =	$691.03		$762.2701	$762.27	$762.30	$762.20