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	$162.52	7.210%	$174.2377	$174.24	$174.25	$174.20
Purchase #2	$34.32	12.589%	$38.6405	$38.64	$38.65	$38.60
Purchase #3	$12.28	12.822%	$13.8545	$13.85	$13.85	$13.90
Purchase #4	$193.91	5.178%	$203.9507	$203.95	$203.95	$204.00
Purchase #5	$101.55	10.125%	$111.8319	$111.83	$111.85	$111.80
Purchase #6	$40.88	5.525%	$43.1386	$43.14	$43.15	$43.10
Purchase #7	$166.58	11.559%	$185.835	$185.84	$185.85	$185.80
7 purchase totals =	$712.04		$771.4889	$771.49	$771.55	$771.40