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	$17.49	10.208%	$19.2754	$19.28	$19.30	$19.30
Purchase #2	$155.52	10.851%	$172.3955	$172.40	$172.40	$172.40
Purchase #3	$117.56	5.664%	$124.2186	$124.22	$124.20	$124.20
Purchase #4	$55.87	13.470%	$63.3957	$63.40	$63.40	$63.40
Purchase #5	$243.61	9.141%	$265.8784	$265.88	$265.90	$265.90
Purchase #6	$6.82	11.279%	$7.5892	$7.59	$7.60	$7.60
Purchase #7	$121.66	4.726%	$127.4097	$127.41	$127.40	$127.40
7 purchase totals =	$718.53		$780.1625	$780.18	$780.20	$780.20