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	$137.53	5.863%	$145.5934	$145.59	$145.60	$145.60
Purchase #2	$212.68	3.802%	$220.7661	$220.77	$220.75	$220.80
Purchase #3	$138.92	9.179%	$151.6715	$151.67	$151.65	$151.70
Purchase #4	$96.64	6.863%	$103.2724	$103.27	$103.25	$103.30
Purchase #5	$41.82	5.733%	$44.2175	$44.22	$44.20	$44.20
Purchase #6	$221.72	10.181%	$244.2933	$244.29	$244.30	$244.30
Purchase #7	$127.55	3.416%	$131.9071	$131.91	$131.90	$131.90
7 purchase totals =	$976.86		$1,041.7213	$1,041.72	$1,041.65	$1,041.80