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	$144.66	5.776%	$153.0156	$153.02	$153.00	$153.00
Purchase #2	$40.63	5.394%	$42.8216	$42.82	$42.80	$42.80
Purchase #3	$46.44	7.791%	$50.0581	$50.06	$50.05	$50.10
Purchase #4	$227.52	10.624%	$251.6917	$251.69	$251.70	$251.70
Purchase #5	$19.47	10.615%	$21.5367	$21.54	$21.55	$21.50
Purchase #6	$123.26	11.386%	$137.2944	$137.29	$137.30	$137.30
Purchase #7	$106.70	4.588%	$111.5954	$111.60	$111.60	$111.60
7 purchase totals =	$708.68		$768.0135	$768.02	$768.00	$768.00