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	$174.82	5.861%	$185.0662	$185.07	$185.05	$185.10
Purchase #2	$132.85	6.646%	$141.6792	$141.68	$141.70	$141.70
Purchase #3	$172.88	13.525%	$196.262	$196.26	$196.25	$196.30
Purchase #4	$74.51	4.762%	$78.0582	$78.06	$78.05	$78.10
Purchase #5	$57.44	3.305%	$59.3384	$59.34	$59.35	$59.30
Purchase #6	$93.71	7.485%	$100.7242	$100.72	$100.70	$100.70
Purchase #7	$244.90	13.699%	$278.4489	$278.45	$278.45	$278.40
7 purchase totals =	$951.11		$1,039.5771	$1,039.58	$1,039.55	$1,039.60