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	$160.39	13.617%	$182.2303	$182.23	$182.25	$182.20
Purchase #2	$90.84	8.159%	$98.2516	$98.25	$98.25	$98.30
Purchase #3	$205.72	13.395%	$233.2762	$233.28	$233.30	$233.30
Purchase #4	$162.63	3.658%	$168.579	$168.58	$168.60	$168.60
Purchase #5	$224.33	13.294%	$254.1524	$254.15	$254.15	$254.20
Purchase #6	$106.75	11.174%	$118.6782	$118.68	$118.70	$118.70
Purchase #7	$126.25	3.383%	$130.521	$130.52	$130.50	$130.50
7 purchase totals =	$1,076.91		$1,185.6887	$1,185.69	$1,185.75	$1,185.80