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	$164.89	5.408%	$173.8073	$173.81	$173.80	$173.80
Purchase #2	$99.96	8.321%	$108.2777	$108.28	$108.30	$108.30
Purchase #3	$132.88	7.598%	$142.9762	$142.98	$143.00	$143.00
Purchase #4	$103.64	8.111%	$112.0462	$112.05	$112.05	$112.00
Purchase #5	$126.52	9.776%	$138.8886	$138.89	$138.90	$138.90
Purchase #6	$125.31	12.777%	$141.3209	$141.32	$141.30	$141.30
Purchase #7	$232.30	5.137%	$244.2333	$244.23	$244.25	$244.20
7 purchase totals =	$985.50		$1,061.5502	$1,061.56	$1,061.60	$1,061.50