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	$164.82	11.350%	$183.5271	$183.53	$183.55	$183.50
Purchase #2	$214.98	12.784%	$242.463	$242.46	$242.45	$242.50
Purchase #3	$221.89	3.562%	$229.7937	$229.79	$229.80	$229.80
Purchase #4	$166.41	4.182%	$173.3693	$173.37	$173.35	$173.40
Purchase #5	$42.72	10.592%	$47.2449	$47.24	$47.25	$47.20
Purchase #6	$140.51	13.264%	$159.1472	$159.15	$159.15	$159.10
Purchase #7	$155.36	3.663%	$161.0508	$161.05	$161.05	$161.10
7 purchase totals =	$1,106.69		$1,196.5960	$1,196.59	$1,196.60	$1,196.60