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	$167.61	13.549%	$190.3195	$190.32	$190.30	$190.30
Purchase #2	$59.78	13.117%	$67.6213	$67.62	$67.60	$67.60
Purchase #3	$109.86	5.835%	$116.2703	$116.27	$116.25	$116.30
Purchase #4	$79.32	4.866%	$83.1797	$83.18	$83.20	$83.20
Purchase #5	$110.84	12.153%	$124.3104	$124.31	$124.30	$124.30
Purchase #6	$153.87	12.462%	$173.0453	$173.05	$173.05	$173.00
Purchase #7	$143.94	12.550%	$162.0045	$162.00	$162.00	$162.00
7 purchase totals =	$825.22		$916.7510	$916.75	$916.70	$916.70