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	$150.88	10.685%	$167.0015	$167.00	$167.00	$167.00
Purchase #2	$150.82	7.826%	$162.6232	$162.62	$162.60	$162.60
Purchase #3	$162.81	7.121%	$174.4037	$174.40	$174.40	$174.40
Purchase #4	$123.73	12.298%	$138.9463	$138.95	$138.95	$138.90
Purchase #5	$203.42	9.239%	$222.214	$222.21	$222.20	$222.20
Purchase #6	$101.60	3.472%	$105.1276	$105.13	$105.15	$105.10
Purchase #7	$127.42	11.783%	$142.4339	$142.43	$142.45	$142.40
7 purchase totals =	$1,020.68		$1,112.7502	$1,112.74	$1,112.75	$1,112.60