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	$201.64	11.513%	$224.8548	$224.85	$224.85	$224.90
Purchase #2	$22.60	11.863%	$25.281	$25.28	$25.30	$25.30
Purchase #3	$54.61	10.492%	$60.3397	$60.34	$60.35	$60.30
Purchase #4	$35.59	12.847%	$40.1622	$40.16	$40.15	$40.20
Purchase #5	$118.84	6.403%	$126.4493	$126.45	$126.45	$126.40
Purchase #6	$94.45	6.320%	$100.4192	$100.42	$100.40	$100.40
Purchase #7	$238.44	12.823%	$269.0152	$269.02	$269.00	$269.00
7 purchase totals =	$766.17		$846.5214	$846.52	$846.50	$846.50