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	$162.94	13.525%	$184.9776	$184.98	$185.00	$185.00
Purchase #2	$61.74	9.286%	$67.4732	$67.47	$67.45	$67.50
Purchase #3	$57.71	7.143%	$61.8322	$61.83	$61.85	$61.80
Purchase #4	$241.52	8.321%	$261.6169	$261.62	$261.60	$261.60
Purchase #5	$45.45	12.846%	$51.2885	$51.29	$51.30	$51.30
Purchase #6	$159.83	7.225%	$171.3777	$171.38	$171.40	$171.40
Purchase #7	$176.92	13.429%	$200.6786	$200.68	$200.70	$200.70
7 purchase totals =	$906.11		$999.2447	$999.25	$999.30	$999.30