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	$111.45	6.581%	$118.7845	$118.78	$118.80	$118.80
Purchase #2	$141.68	9.604%	$155.2869	$155.29	$155.30	$155.30
Purchase #3	$239.58	13.805%	$272.654	$272.65	$272.65	$272.70
Purchase #4	$212.55	6.807%	$227.0183	$227.02	$227.00	$227.00
Purchase #5	$34.69	10.300%	$38.2631	$38.26	$38.25	$38.30
Purchase #6	$106.79	4.467%	$111.5603	$111.56	$111.55	$111.60
Purchase #7	$50.48	8.614%	$54.8283	$54.83	$54.85	$54.80
7 purchase totals =	$897.22		$978.3954	$978.39	$978.40	$978.50