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	$173.79	7.188%	$186.282	$186.28	$186.30	$186.30
Purchase #2	$239.25	4.252%	$249.4229	$249.42	$249.40	$249.40
Purchase #3	$143.86	8.703%	$156.3801	$156.38	$156.40	$156.40
Purchase #4	$85.92	4.676%	$89.9376	$89.94	$89.95	$89.90
Purchase #5	$237.38	8.804%	$258.2789	$258.28	$258.30	$258.30
Purchase #6	$212.56	10.850%	$235.6228	$235.62	$235.60	$235.60
Purchase #7	$238.67	6.242%	$253.5678	$253.57	$253.55	$253.60
7 purchase totals =	$1,331.43		$1,429.4921	$1,429.49	$1,429.50	$1,429.50