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	$64.74	11.847%	$72.4097	$72.41	$72.40	$72.40
Purchase #2	$223.86	6.158%	$237.6453	$237.65	$237.65	$237.60
Purchase #3	$132.54	8.725%	$144.1041	$144.10	$144.10	$144.10
Purchase #4	$248.92	11.227%	$276.8662	$276.87	$276.85	$276.90
Purchase #5	$187.45	3.843%	$194.6537	$194.65	$194.65	$194.70
Purchase #6	$52.57	13.756%	$59.8015	$59.80	$59.80	$59.80
Purchase #7	$139.89	4.137%	$145.6772	$145.68	$145.70	$145.70
7 purchase totals =	$1,049.97		$1,131.1577	$1,131.16	$1,131.15	$1,131.20