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	$57.99	13.687%	$65.9271	$65.93	$65.95	$65.90
Purchase #2	$19.98	12.694%	$22.5163	$22.52	$22.50	$22.50
Purchase #3	$134.25	12.810%	$151.4474	$151.45	$151.45	$151.40
Purchase #4	$216.92	12.654%	$244.3691	$244.37	$244.35	$244.40
Purchase #5	$59.60	3.702%	$61.8064	$61.81	$61.80	$61.80
Purchase #6	$112.69	13.385%	$127.7736	$127.77	$127.75	$127.80
Purchase #7	$245.76	11.224%	$273.3441	$273.34	$273.35	$273.30
7 purchase totals =	$847.19		$947.1840	$947.19	$947.15	$947.10