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	$224.81	7.497%	$241.664	$241.66	$241.65	$241.70
Purchase #2	$154.53	11.405%	$172.1541	$172.15	$172.15	$172.20
Purchase #3	$14.28	7.535%	$15.356	$15.36	$15.35	$15.40
Purchase #4	$115.38	10.256%	$127.2134	$127.21	$127.20	$127.20
Purchase #5	$209.91	4.533%	$219.4252	$219.43	$219.45	$219.40
Purchase #6	$110.98	5.314%	$116.8775	$116.88	$116.90	$116.90
Purchase #7	$89.82	13.683%	$102.1101	$102.11	$102.10	$102.10
7 purchase totals =	$919.71		$994.8003	$994.80	$994.80	$994.90