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	$38.47	11.858%	$43.0318	$43.03	$43.05	$43.00
Purchase #2	$140.54	3.610%	$145.6135	$145.61	$145.60	$145.60
Purchase #3	$204.33	10.533%	$225.8521	$225.85	$225.85	$225.90
Purchase #4	$50.28	3.707%	$52.1439	$52.14	$52.15	$52.10
Purchase #5	$149.91	6.515%	$159.6766	$159.68	$159.70	$159.70
Purchase #6	$175.56	5.858%	$185.8443	$185.84	$185.85	$185.80
Purchase #7	$174.50	11.694%	$194.906	$194.91	$194.90	$194.90
7 purchase totals =	$933.59		$1,007.0682	$1,007.06	$1,007.10	$1,007.00