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	$226.72	8.328%	$245.6012	$245.60	$245.60	$245.60
Purchase #2	$154.52	12.282%	$173.4981	$173.50	$173.50	$173.50
Purchase #3	$44.74	13.836%	$50.9302	$50.93	$50.95	$50.90
Purchase #4	$26.73	6.223%	$28.3934	$28.39	$28.40	$28.40
Purchase #5	$97.50	7.782%	$105.0875	$105.09	$105.10	$105.10
Purchase #6	$158.43	9.532%	$173.5315	$173.53	$173.55	$173.50
Purchase #7	$227.55	12.591%	$256.2008	$256.20	$256.20	$256.20
7 purchase totals =	$936.19		$1,033.2427	$1,033.24	$1,033.30	$1,033.20