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	$155.91	5.494%	$164.4757	$164.48	$164.50	$164.50
Purchase #2	$10.26	10.132%	$11.2995	$11.30	$11.30	$11.30
Purchase #3	$209.83	9.749%	$230.2863	$230.29	$230.30	$230.30
Purchase #4	$242.43	6.662%	$258.5807	$258.58	$258.60	$258.60
Purchase #5	$38.47	6.115%	$40.8224	$40.82	$40.80	$40.80
Purchase #6	$172.45	6.619%	$183.8645	$183.86	$183.85	$183.90
Purchase #7	$75.89	3.819%	$78.7882	$78.79	$78.80	$78.80
7 purchase totals =	$905.24		$968.1173	$968.12	$968.15	$968.20