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	$174.58	5.181%	$183.625	$183.63	$183.65	$183.60
Purchase #2	$162.58	10.729%	$180.0232	$180.02	$180.00	$180.00
Purchase #3	$139.39	8.629%	$151.418	$151.42	$151.40	$151.40
Purchase #4	$146.56	4.568%	$153.2549	$153.25	$153.25	$153.30
Purchase #5	$238.29	4.312%	$248.5651	$248.57	$248.55	$248.60
Purchase #6	$108.27	3.328%	$111.8732	$111.87	$111.85	$111.90
Purchase #7	$68.44	3.372%	$70.7478	$70.75	$70.75	$70.70
7 purchase totals =	$1,038.11		$1,099.5072	$1,099.51	$1,099.45	$1,099.50