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	$159.53	9.245%	$174.2785	$174.28	$174.30	$174.30
Purchase #2	$138.48	11.349%	$154.1961	$154.20	$154.20	$154.20
Purchase #3	$159.40	10.176%	$175.6205	$175.62	$175.60	$175.60
Purchase #4	$71.97	7.561%	$77.4117	$77.41	$77.40	$77.40
Purchase #5	$101.89	7.237%	$109.2638	$109.26	$109.25	$109.30
Purchase #6	$140.41	13.141%	$158.8613	$158.86	$158.85	$158.90
Purchase #7	$136.65	11.624%	$152.5342	$152.53	$152.55	$152.50
7 purchase totals =	$908.33		$1,002.1661	$1,002.16	$1,002.15	$1,002.20