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	$33.83	5.744%	$35.7732	$35.77	$35.75	$35.80
Purchase #2	$235.98	11.114%	$262.2068	$262.21	$262.20	$262.20
Purchase #3	$17.54	10.521%	$19.3854	$19.39	$19.40	$19.40
Purchase #4	$81.87	9.332%	$89.5101	$89.51	$89.50	$89.50
Purchase #5	$157.40	11.375%	$175.3043	$175.30	$175.30	$175.30
Purchase #6	$229.51	9.642%	$251.6394	$251.64	$251.65	$251.60
Purchase #7	$40.85	4.573%	$42.7181	$42.72	$42.70	$42.70
7 purchase totals =	$796.98		$876.5373	$876.54	$876.50	$876.50