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	$54.65	11.340%	$60.8473	$60.85	$60.85	$60.80
Purchase #2	$124.44	8.160%	$134.5943	$134.59	$134.60	$134.60
Purchase #3	$123.58	12.707%	$139.2833	$139.28	$139.30	$139.30
Purchase #4	$241.35	5.486%	$254.5905	$254.59	$254.60	$254.60
Purchase #5	$127.72	7.244%	$136.972	$136.97	$136.95	$137.00
Purchase #6	$179.30	3.595%	$185.7458	$185.75	$185.75	$185.70
Purchase #7	$92.63	13.687%	$105.3083	$105.31	$105.30	$105.30
7 purchase totals =	$943.67		$1,017.3415	$1,017.34	$1,017.35	$1,017.30