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	$61.93	7.671%	$66.6807	$66.68	$66.70	$66.70
Purchase #2	$216.65	13.264%	$245.3865	$245.39	$245.40	$245.40
Purchase #3	$48.32	3.244%	$49.8875	$49.89	$49.90	$49.90
Purchase #4	$45.67	5.393%	$48.133	$48.13	$48.15	$48.10
Purchase #5	$162.59	7.121%	$174.168	$174.17	$174.15	$174.20
Purchase #6	$50.46	4.735%	$52.8493	$52.85	$52.85	$52.80
Purchase #7	$102.60	13.406%	$116.3546	$116.35	$116.35	$116.40
7 purchase totals =	$688.22		$753.4596	$753.46	$753.50	$753.50