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	$95.65	4.357%	$99.8175	$99.82	$99.80	$99.80
Purchase #2	$34.94	7.604%	$37.5968	$37.60	$37.60	$37.60
Purchase #3	$35.37	6.798%	$37.7745	$37.77	$37.75	$37.80
Purchase #4	$218.33	5.390%	$230.098	$230.10	$230.10	$230.10
Purchase #5	$201.27	12.699%	$226.8293	$226.83	$226.85	$226.80
Purchase #6	$120.44	10.231%	$132.7622	$132.76	$132.75	$132.80
Purchase #7	$38.74	6.605%	$41.2988	$41.30	$41.30	$41.30
7 purchase totals =	$744.74		$806.1771	$806.18	$806.15	$806.20