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	$173.30	13.214%	$196.1999	$196.20	$196.20	$196.20
Purchase #2	$143.91	8.623%	$156.3194	$156.32	$156.30	$156.30
Purchase #3	$215.55	13.395%	$244.4229	$244.42	$244.40	$244.40
Purchase #4	$6.45	10.747%	$7.1432	$7.14	$7.15	$7.10
Purchase #5	$92.43	3.810%	$95.9516	$95.95	$95.95	$96.00
Purchase #6	$21.32	12.311%	$23.9447	$23.94	$23.95	$23.90
Purchase #7	$67.72	6.517%	$72.1333	$72.13	$72.15	$72.10
7 purchase totals =	$720.68		$796.1150	$796.10	$796.10	$796.00