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	$211.71	5.463%	$223.2757	$223.28	$223.30	$223.30
Purchase #2	$230.79	5.151%	$242.678	$242.68	$242.70	$242.70
Purchase #3	$127.84	13.131%	$144.6267	$144.63	$144.65	$144.60
Purchase #4	$216.40	11.156%	$240.5416	$240.54	$240.55	$240.50
Purchase #5	$61.83	5.262%	$65.0835	$65.08	$65.10	$65.10
Purchase #6	$123.91	5.602%	$130.8514	$130.85	$130.85	$130.90
Purchase #7	$9.40	4.542%	$9.8269	$9.83	$9.85	$9.80
7 purchase totals =	$981.88		$1,056.8838	$1,056.89	$1,057.00	$1,056.90