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	$233.45	8.834%	$254.073	$254.07	$254.05	$254.10
Purchase #2	$170.37	10.513%	$188.281	$188.28	$188.30	$188.30
Purchase #3	$101.67	7.510%	$109.3054	$109.31	$109.30	$109.30
Purchase #4	$196.42	7.840%	$211.8193	$211.82	$211.80	$211.80
Purchase #5	$145.70	11.239%	$162.0752	$162.08	$162.10	$162.10
Purchase #6	$214.42	12.814%	$241.8958	$241.90	$241.90	$241.90
Purchase #7	$11.29	13.602%	$12.8257	$12.83	$12.85	$12.80
7 purchase totals =	$1,073.32		$1,180.2754	$1,180.29	$1,180.30	$1,180.30