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	$177.30	13.314%	$200.9057	$200.91	$200.90	$200.90
Purchase #2	$222.56	9.773%	$244.3108	$244.31	$244.30	$244.30
Purchase #3	$107.76	3.578%	$111.6157	$111.62	$111.60	$111.60
Purchase #4	$52.39	13.786%	$59.6125	$59.61	$59.60	$59.60
Purchase #5	$28.86	13.348%	$32.7122	$32.71	$32.70	$32.70
Purchase #6	$224.34	13.123%	$253.7801	$253.78	$253.80	$253.80
Purchase #7	$241.48	4.712%	$252.8585	$252.86	$252.85	$252.90
7 purchase totals =	$1,054.69		$1,155.7955	$1,155.80	$1,155.75	$1,155.80