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	$98.39	13.604%	$111.775	$111.78	$111.80	$111.80
Purchase #2	$24.74	9.660%	$27.1299	$27.13	$27.15	$27.10
Purchase #3	$233.37	3.646%	$241.8787	$241.88	$241.90	$241.90
Purchase #4	$104.72	3.530%	$108.4166	$108.42	$108.40	$108.40
Purchase #5	$160.31	11.479%	$178.712	$178.71	$178.70	$178.70
Purchase #6	$37.64	11.209%	$41.8591	$41.86	$41.85	$41.90
Purchase #7	$246.84	7.850%	$266.2169	$266.22	$266.20	$266.20
7 purchase totals =	$906.01		$975.9882	$976.00	$976.00	$976.00