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	$62.76	8.105%	$67.8467	$67.85	$67.85	$67.80
Purchase #2	$159.90	3.629%	$165.7028	$165.70	$165.70	$165.70
Purchase #3	$164.31	4.835%	$172.2544	$172.25	$172.25	$172.30
Purchase #4	$193.76	13.486%	$219.8905	$219.89	$219.90	$219.90
Purchase #5	$146.70	4.556%	$153.3837	$153.38	$153.40	$153.40
Purchase #6	$233.31	3.601%	$241.7115	$241.71	$241.70	$241.70
Purchase #7	$209.67	10.783%	$232.2787	$232.28	$232.30	$232.30
7 purchase totals =	$1,170.41		$1,253.0683	$1,253.06	$1,253.10	$1,253.10