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	$114.51	11.122%	$127.2458	$127.25	$127.25	$127.20
Purchase #2	$99.42	3.770%	$103.1681	$103.17	$103.15	$103.20
Purchase #3	$9.35	5.381%	$9.8531	$9.85	$9.85	$9.90
Purchase #4	$79.45	13.438%	$90.1265	$90.13	$90.15	$90.10
Purchase #5	$153.30	5.800%	$162.1914	$162.19	$162.20	$162.20
Purchase #6	$241.32	13.242%	$273.2756	$273.28	$273.30	$273.30
Purchase #7	$153.29	11.852%	$171.4579	$171.46	$171.45	$171.50
7 purchase totals =	$850.64		$937.3184	$937.33	$937.35	$937.40