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	$103.42	8.584%	$112.2976	$112.30	$112.30	$112.30
Purchase #2	$208.75	10.109%	$229.8525	$229.85	$229.85	$229.90
Purchase #3	$103.76	4.632%	$108.5662	$108.57	$108.55	$108.60
Purchase #4	$58.82	10.765%	$65.152	$65.15	$65.15	$65.20
Purchase #5	$182.46	11.131%	$202.7696	$202.77	$202.75	$202.80
Purchase #6	$86.96	4.208%	$90.6193	$90.62	$90.60	$90.60
Purchase #7	$214.86	7.208%	$230.3471	$230.35	$230.35	$230.30
7 purchase totals =	$959.03		$1,039.6043	$1,039.61	$1,039.55	$1,039.70