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	$97.28	11.204%	$108.1793	$108.18	$108.20	$108.20
Purchase #2	$96.92	12.404%	$108.942	$108.94	$108.95	$108.90
Purchase #3	$200.63	10.520%	$221.7363	$221.74	$221.75	$221.70
Purchase #4	$89.59	11.568%	$99.9538	$99.95	$99.95	$100.00
Purchase #5	$105.91	5.223%	$111.4417	$111.44	$111.45	$111.40
Purchase #6	$247.35	6.162%	$262.5917	$262.59	$262.60	$262.60
Purchase #7	$231.59	13.427%	$262.6856	$262.69	$262.70	$262.70
7 purchase totals =	$1,069.27		$1,175.5304	$1,175.53	$1,175.60	$1,175.50