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	$95.92	10.592%	$106.0798	$106.08	$106.10	$106.10
Purchase #2	$222.29	3.407%	$229.8634	$229.86	$229.85	$229.90
Purchase #3	$225.58	12.671%	$254.1632	$254.16	$254.15	$254.20
Purchase #4	$168.69	5.697%	$178.3003	$178.30	$178.30	$178.30
Purchase #5	$243.75	4.799%	$255.4476	$255.45	$255.45	$255.40
Purchase #6	$108.52	7.327%	$116.4713	$116.47	$116.45	$116.50
Purchase #7	$61.90	9.618%	$67.8535	$67.85	$67.85	$67.90
7 purchase totals =	$1,126.65		$1,208.1791	$1,208.17	$1,208.15	$1,208.30