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	$162.92	8.404%	$176.6118	$176.61	$176.60	$176.60
Purchase #2	$154.56	9.642%	$169.4627	$169.46	$169.45	$169.50
Purchase #3	$174.58	13.793%	$198.6598	$198.66	$198.65	$198.70
Purchase #4	$131.79	10.827%	$146.0589	$146.06	$146.05	$146.10
Purchase #5	$250.59	11.443%	$279.265	$279.27	$279.25	$279.30
Purchase #6	$43.91	6.646%	$46.8283	$46.83	$46.85	$46.80
Purchase #7	$54.92	10.643%	$60.7651	$60.77	$60.75	$60.80
7 purchase totals =	$973.27		$1,077.6516	$1,077.66	$1,077.60	$1,077.80