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	$127.59	5.553%	$134.6751	$134.68	$134.70	$134.70
Purchase #2	$94.49	5.712%	$99.8873	$99.89	$99.90	$99.90
Purchase #3	$198.71	7.825%	$214.2591	$214.26	$214.25	$214.30
Purchase #4	$146.89	9.528%	$160.8857	$160.89	$160.90	$160.90
Purchase #5	$184.63	13.841%	$210.1846	$210.18	$210.20	$210.20
Purchase #6	$40.67	4.787%	$42.6169	$42.62	$42.60	$42.60
Purchase #7	$5.29	6.635%	$5.641	$5.64	$5.65	$5.60
7 purchase totals =	$798.27		$868.1497	$868.16	$868.20	$868.20