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	$166.48	6.525%	$177.3428	$177.34	$177.35	$177.30
Purchase #2	$14.26	9.408%	$15.6016	$15.60	$15.60	$15.60
Purchase #3	$234.48	3.147%	$241.8591	$241.86	$241.85	$241.90
Purchase #4	$201.31	4.469%	$210.3065	$210.31	$210.30	$210.30
Purchase #5	$55.30	9.671%	$60.6481	$60.65	$60.65	$60.60
Purchase #6	$101.91	9.297%	$111.3846	$111.38	$111.40	$111.40
Purchase #7	$233.73	4.686%	$244.6826	$244.68	$244.70	$244.70
7 purchase totals =	$1,007.47		$1,061.8253	$1,061.82	$1,061.85	$1,061.80