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	$139.92	9.544%	$153.274	$153.27	$153.25	$153.30
Purchase #2	$229.33	13.727%	$260.8101	$260.81	$260.80	$260.80
Purchase #3	$244.30	9.548%	$267.6258	$267.63	$267.65	$267.60
Purchase #4	$43.39	5.117%	$45.6103	$45.61	$45.60	$45.60
Purchase #5	$42.83	5.528%	$45.1976	$45.20	$45.20	$45.20
Purchase #6	$155.46	9.108%	$169.6193	$169.62	$169.60	$169.60
Purchase #7	$184.47	13.170%	$208.7647	$208.76	$208.75	$208.80
7 purchase totals =	$1,039.70		$1,150.9018	$1,150.90	$1,150.85	$1,150.90