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	$54.58	5.627%	$57.6512	$57.65	$57.65	$57.70
Purchase #2	$207.65	10.701%	$229.8706	$229.87	$229.85	$229.90
Purchase #3	$9.78	7.690%	$10.5321	$10.53	$10.55	$10.50
Purchase #4	$78.30	5.459%	$82.5744	$82.57	$82.55	$82.60
Purchase #5	$108.27	3.518%	$112.0789	$112.08	$112.10	$112.10
Purchase #6	$49.58	9.195%	$54.1389	$54.14	$54.15	$54.10
Purchase #7	$51.80	9.269%	$56.6013	$56.60	$56.60	$56.60
7 purchase totals =	$559.96		$603.4474	$603.44	$603.45	$603.50