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	$10.56	9.249%	$11.5367	$11.54	$11.55	$11.50
Purchase #2	$111.91	10.123%	$123.2386	$123.24	$123.25	$123.20
Purchase #3	$37.70	5.334%	$39.7109	$39.71	$39.70	$39.70
Purchase #4	$69.62	5.388%	$73.3711	$73.37	$73.35	$73.40
Purchase #5	$90.47	9.630%	$99.1823	$99.18	$99.20	$99.20
Purchase #6	$249.61	13.811%	$284.0836	$284.08	$284.10	$284.10
Purchase #7	$140.37	3.693%	$145.5539	$145.55	$145.55	$145.60
7 purchase totals =	$710.24		$776.6771	$776.67	$776.70	$776.70