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	$212.52	4.379%	$221.8263	$221.83	$221.85	$221.80
Purchase #2	$134.80	4.664%	$141.0871	$141.09	$141.10	$141.10
Purchase #3	$235.83	3.103%	$243.1478	$243.15	$243.15	$243.10
Purchase #4	$162.37	6.138%	$172.3363	$172.34	$172.35	$172.30
Purchase #5	$139.82	8.326%	$151.4614	$151.46	$151.45	$151.50
Purchase #6	$88.92	6.609%	$94.7967	$94.80	$94.80	$94.80
Purchase #7	$30.90	4.644%	$32.335	$32.34	$32.35	$32.30
7 purchase totals =	$1,005.16		$1,056.9906	$1,057.01	$1,057.05	$1,056.90