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	$181.76	12.582%	$204.629	$204.63	$204.65	$204.60
Purchase #2	$250.71	13.310%	$284.0795	$284.08	$284.10	$284.10
Purchase #3	$105.49	5.340%	$111.1232	$111.12	$111.10	$111.10
Purchase #4	$61.98	5.272%	$65.2476	$65.25	$65.25	$65.20
Purchase #5	$180.51	8.238%	$195.3804	$195.38	$195.40	$195.40
Purchase #6	$174.94	5.801%	$185.0883	$185.09	$185.10	$185.10
Purchase #7	$236.93	6.103%	$251.3898	$251.39	$251.40	$251.40
7 purchase totals =	$1,192.32		$1,296.9378	$1,296.94	$1,297.00	$1,296.90