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	$230.28	5.627%	$243.2379	$243.24	$243.25	$243.20
Purchase #2	$77.83	13.587%	$88.4048	$88.40	$88.40	$88.40
Purchase #3	$161.69	6.867%	$172.7933	$172.79	$172.80	$172.80
Purchase #4	$62.40	6.827%	$66.66	$66.66	$66.65	$66.70
Purchase #5	$209.71	11.408%	$233.6337	$233.63	$233.65	$233.60
Purchase #6	$43.74	4.227%	$45.5889	$45.59	$45.60	$45.60
Purchase #7	$49.41	3.337%	$51.0588	$51.06	$51.05	$51.10
7 purchase totals =	$835.06		$901.3774	$901.37	$901.40	$901.40