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	$57.29	9.314%	$62.626	$62.63	$62.65	$62.60
Purchase #2	$239.46	4.274%	$249.6945	$249.69	$249.70	$249.70
Purchase #3	$161.93	5.512%	$170.8556	$170.86	$170.85	$170.90
Purchase #4	$69.42	4.145%	$72.2975	$72.30	$72.30	$72.30
Purchase #5	$114.38	8.301%	$123.8747	$123.87	$123.85	$123.90
Purchase #6	$16.80	10.684%	$18.5949	$18.59	$18.60	$18.60
Purchase #7	$36.80	3.729%	$38.1723	$38.17	$38.15	$38.20
7 purchase totals =	$696.08		$736.1155	$736.11	$736.10	$736.20