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	$98.99	12.189%	$111.0559	$111.06	$111.05	$111.10
Purchase #2	$169.39	4.794%	$177.5106	$177.51	$177.50	$177.50
Purchase #3	$139.65	9.735%	$153.2449	$153.24	$153.25	$153.20
Purchase #4	$75.80	3.674%	$78.5849	$78.58	$78.60	$78.60
Purchase #5	$78.30	10.673%	$86.657	$86.66	$86.65	$86.70
Purchase #6	$222.54	9.629%	$243.9684	$243.97	$243.95	$244.00
Purchase #7	$38.70	11.860%	$43.2898	$43.29	$43.30	$43.30
7 purchase totals =	$823.37		$894.3115	$894.31	$894.30	$894.40