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	$172.80	3.766%	$179.3076	$179.31	$179.30	$179.30
Purchase #2	$181.86	12.476%	$204.5489	$204.55	$204.55	$204.50
Purchase #3	$191.95	6.863%	$205.1235	$205.12	$205.10	$205.10
Purchase #4	$127.41	4.577%	$133.2416	$133.24	$133.25	$133.20
Purchase #5	$96.50	7.569%	$103.8041	$103.80	$103.80	$103.80
Purchase #6	$125.97	4.595%	$131.7583	$131.76	$131.75	$131.80
Purchase #7	$177.56	8.570%	$192.7769	$192.78	$192.80	$192.80
7 purchase totals =	$1,074.05		$1,150.5609	$1,150.56	$1,150.55	$1,150.50