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	$11.47	7.237%	$12.3001	$12.30	$12.30	$12.30
Purchase #2	$222.29	7.625%	$239.2396	$239.24	$239.25	$239.20
Purchase #3	$182.46	6.871%	$194.9968	$195.00	$195.00	$195.00
Purchase #4	$143.35	7.138%	$153.5823	$153.58	$153.60	$153.60
Purchase #5	$35.47	11.306%	$39.4802	$39.48	$39.50	$39.50
Purchase #6	$65.95	10.111%	$72.6182	$72.62	$72.60	$72.60
Purchase #7	$79.52	13.584%	$90.322	$90.32	$90.30	$90.30
7 purchase totals =	$740.51		$802.5392	$802.54	$802.55	$802.50