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	$20.32	7.374%	$21.8184	$21.82	$21.80	$21.80
Purchase #2	$59.38	5.123%	$62.422	$62.42	$62.40	$62.40
Purchase #3	$157.28	7.638%	$169.293	$169.29	$169.30	$169.30
Purchase #4	$167.35	8.829%	$182.1253	$182.13	$182.15	$182.10
Purchase #5	$227.83	12.350%	$255.967	$255.97	$255.95	$256.00
Purchase #6	$162.60	3.229%	$167.8504	$167.85	$167.85	$167.90
Purchase #7	$224.64	13.370%	$254.6744	$254.67	$254.65	$254.70
7 purchase totals =	$1,019.40		$1,114.1505	$1,114.15	$1,114.10	$1,114.20