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	$223.81	9.300%	$244.6243	$244.62	$244.60	$244.60
Purchase #2	$137.28	12.739%	$154.7681	$154.77	$154.75	$154.80
Purchase #3	$133.77	3.478%	$138.4225	$138.42	$138.40	$138.40
Purchase #4	$118.51	7.245%	$127.096	$127.10	$127.10	$127.10
Purchase #5	$55.43	11.523%	$61.8172	$61.82	$61.80	$61.80
Purchase #6	$101.27	11.806%	$113.2259	$113.23	$113.25	$113.20
Purchase #7	$24.59	11.518%	$27.4223	$27.42	$27.40	$27.40
7 purchase totals =	$794.66		$867.3763	$867.38	$867.30	$867.30