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	$238.28	7.233%	$255.5148	$255.51	$255.50	$255.50
Purchase #2	$50.34	3.299%	$52.0007	$52.00	$52.00	$52.00
Purchase #3	$87.94	5.415%	$92.702	$92.70	$92.70	$92.70
Purchase #4	$28.39	13.845%	$32.3206	$32.32	$32.30	$32.30
Purchase #5	$104.47	13.732%	$118.8158	$118.82	$118.80	$118.80
Purchase #6	$200.37	5.423%	$211.2361	$211.24	$211.25	$211.20
Purchase #7	$33.40	4.857%	$35.0222	$35.02	$35.00	$35.00
7 purchase totals =	$743.19		$797.6122	$797.61	$797.55	$797.50