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	$119.34	10.716%	$132.1285	$132.13	$132.15	$132.10
Purchase #2	$56.73	4.739%	$59.4184	$59.42	$59.40	$59.40
Purchase #3	$12.60	8.224%	$13.6362	$13.64	$13.65	$13.60
Purchase #4	$170.75	6.534%	$181.9068	$181.91	$181.90	$181.90
Purchase #5	$109.85	5.832%	$116.2565	$116.26	$116.25	$116.30
Purchase #6	$104.27	4.634%	$109.1019	$109.10	$109.10	$109.10
Purchase #7	$228.54	3.839%	$237.3137	$237.31	$237.30	$237.30
7 purchase totals =	$802.08		$849.7620	$849.77	$849.75	$849.70