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	$241.27	8.532%	$261.8552	$261.86	$261.85	$261.90
Purchase #2	$145.26	9.818%	$159.5216	$159.52	$159.50	$159.50
Purchase #3	$236.49	10.462%	$261.2316	$261.23	$261.25	$261.20
Purchase #4	$56.26	5.275%	$59.2277	$59.23	$59.25	$59.20
Purchase #5	$95.53	8.278%	$103.438	$103.44	$103.45	$103.40
Purchase #6	$19.62	4.534%	$20.5096	$20.51	$20.50	$20.50
Purchase #7	$82.29	13.698%	$93.5621	$93.56	$93.55	$93.60
7 purchase totals =	$876.72		$959.3458	$959.35	$959.35	$959.30