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	$123.50	8.269%	$133.7122	$133.71	$133.70	$133.70
Purchase #2	$217.43	10.607%	$240.4928	$240.49	$240.50	$240.50
Purchase #3	$228.81	9.237%	$249.9452	$249.95	$249.95	$249.90
Purchase #4	$108.34	4.832%	$113.575	$113.58	$113.60	$113.60
Purchase #5	$146.33	8.169%	$158.2837	$158.28	$158.30	$158.30
Purchase #6	$101.89	9.762%	$111.8365	$111.84	$111.85	$111.80
Purchase #7	$172.27	4.826%	$180.5838	$180.58	$180.60	$180.60
7 purchase totals =	$1,098.57		$1,188.4292	$1,188.43	$1,188.50	$1,188.40