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	$119.87	10.237%	$132.1411	$132.14	$132.15	$132.10
Purchase #2	$85.79	5.412%	$90.433	$90.43	$90.45	$90.40
Purchase #3	$208.87	3.318%	$215.8003	$215.80	$215.80	$215.80
Purchase #4	$230.67	13.648%	$262.1518	$262.15	$262.15	$262.20
Purchase #5	$69.95	13.485%	$79.3828	$79.38	$79.40	$79.40
Purchase #6	$121.39	4.809%	$127.2276	$127.23	$127.25	$127.20
Purchase #7	$29.84	6.605%	$31.8109	$31.81	$31.80	$31.80
7 purchase totals =	$866.38		$938.9475	$938.94	$939.00	$938.90