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	$143.62	9.151%	$156.7627	$156.76	$156.75	$156.80
Purchase #2	$38.57	3.229%	$39.8154	$39.82	$39.80	$39.80
Purchase #3	$181.25	13.264%	$205.291	$205.29	$205.30	$205.30
Purchase #4	$99.35	5.820%	$105.1322	$105.13	$105.15	$105.10
Purchase #5	$170.47	9.445%	$186.5709	$186.57	$186.55	$186.60
Purchase #6	$11.71	5.295%	$12.33	$12.33	$12.35	$12.30
Purchase #7	$34.92	3.545%	$36.1579	$36.16	$36.15	$36.20
7 purchase totals =	$679.89		$742.0601	$742.06	$742.05	$742.10