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	$211.94	7.269%	$227.3459	$227.35	$227.35	$227.30
Purchase #2	$52.91	6.707%	$56.4587	$56.46	$56.45	$56.50
Purchase #3	$127.68	13.312%	$144.6768	$144.68	$144.70	$144.70
Purchase #4	$237.31	13.545%	$269.4536	$269.45	$269.45	$269.50
Purchase #5	$54.46	9.873%	$59.8368	$59.84	$59.85	$59.80
Purchase #6	$220.84	12.779%	$249.0611	$249.06	$249.05	$249.10
Purchase #7	$125.36	5.761%	$132.582	$132.58	$132.60	$132.60
7 purchase totals =	$1,030.50		$1,139.4149	$1,139.42	$1,139.45	$1,139.50