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	$106.45	4.709%	$111.4627	$111.46	$111.45	$111.50
Purchase #2	$83.98	12.775%	$94.7084	$94.71	$94.70	$94.70
Purchase #3	$89.35	7.420%	$95.9798	$95.98	$96.00	$96.00
Purchase #4	$91.38	11.244%	$101.6548	$101.65	$101.65	$101.70
Purchase #5	$99.87	9.815%	$109.6722	$109.67	$109.65	$109.70
Purchase #6	$127.71	13.855%	$145.4042	$145.40	$145.40	$145.40
Purchase #7	$212.63	8.760%	$231.2564	$231.26	$231.25	$231.30
7 purchase totals =	$811.37		$890.1385	$890.13	$890.10	$890.30