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	$214.79	6.439%	$228.6203	$228.62	$228.60	$228.60
Purchase #2	$146.84	11.211%	$163.3022	$163.30	$163.30	$163.30
Purchase #3	$232.53	11.849%	$260.0825	$260.08	$260.10	$260.10
Purchase #4	$101.60	9.532%	$111.2845	$111.28	$111.30	$111.30
Purchase #5	$139.34	3.611%	$144.3716	$144.37	$144.35	$144.40
Purchase #6	$184.50	8.843%	$200.8153	$200.82	$200.80	$200.80
Purchase #7	$79.59	3.389%	$82.2873	$82.29	$82.30	$82.30
7 purchase totals =	$1,099.19		$1,190.7637	$1,190.76	$1,190.75	$1,190.80