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	$113.52	10.870%	$125.8596	$125.86	$125.85	$125.90
Purchase #2	$171.26	4.316%	$178.6516	$178.65	$178.65	$178.70
Purchase #3	$152.97	9.387%	$167.3293	$167.33	$167.35	$167.30
Purchase #4	$146.56	13.448%	$166.2694	$166.27	$166.25	$166.30
Purchase #5	$84.31	6.657%	$89.9225	$89.92	$89.90	$89.90
Purchase #6	$85.96	4.249%	$89.6124	$89.61	$89.60	$89.60
Purchase #7	$68.45	8.610%	$74.3435	$74.34	$74.35	$74.30
7 purchase totals =	$823.03		$891.9883	$891.98	$891.95	$892.00