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	$101.71	3.666%	$105.4387	$105.44	$105.45	$105.40
Purchase #2	$146.93	10.244%	$161.9815	$161.98	$162.00	$162.00
Purchase #3	$232.93	8.308%	$252.2818	$252.28	$252.30	$252.30
Purchase #4	$141.42	13.367%	$160.3236	$160.32	$160.30	$160.30
Purchase #5	$40.53	3.296%	$41.8659	$41.87	$41.85	$41.90
Purchase #6	$108.51	13.761%	$123.4421	$123.44	$123.45	$123.40
Purchase #7	$38.49	6.128%	$40.8487	$40.85	$40.85	$40.80
7 purchase totals =	$810.52		$886.1823	$886.18	$886.20	$886.10