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	$43.42	3.381%	$44.888	$44.89	$44.90	$44.90
Purchase #2	$20.72	4.525%	$21.6576	$21.66	$21.65	$21.70
Purchase #3	$21.44	5.154%	$22.545	$22.55	$22.55	$22.50
Purchase #4	$139.84	7.378%	$150.1574	$150.16	$150.15	$150.20
Purchase #5	$17.26	5.647%	$18.2347	$18.23	$18.25	$18.20
Purchase #6	$160.33	4.530%	$167.5929	$167.59	$167.60	$167.60
Purchase #7	$231.34	13.752%	$263.1539	$263.15	$263.15	$263.20
7 purchase totals =	$634.35		$688.2295	$688.23	$688.25	$688.30