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	$169.65	6.156%	$180.0937	$180.09	$180.10	$180.10
Purchase #2	$124.91	6.114%	$132.547	$132.55	$132.55	$132.50
Purchase #3	$91.52	13.214%	$103.6135	$103.61	$103.60	$103.60
Purchase #4	$250.56	5.316%	$263.8798	$263.88	$263.90	$263.90
Purchase #5	$13.61	4.853%	$14.2705	$14.27	$14.25	$14.30
Purchase #6	$160.42	4.772%	$168.0752	$168.08	$168.10	$168.10
Purchase #7	$209.72	7.335%	$225.103	$225.10	$225.10	$225.10
7 purchase totals =	$1,020.39		$1,087.5827	$1,087.58	$1,087.60	$1,087.60