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	$101.46	6.302%	$107.854	$107.85	$107.85	$107.90
Purchase #2	$83.60	7.204%	$89.6225	$89.62	$89.60	$89.60
Purchase #3	$153.68	8.847%	$167.2761	$167.28	$167.30	$167.30
Purchase #4	$33.33	5.160%	$35.0498	$35.05	$35.05	$35.00
Purchase #5	$38.50	12.792%	$43.4249	$43.42	$43.40	$43.40
Purchase #6	$29.94	10.823%	$33.1804	$33.18	$33.20	$33.20
Purchase #7	$106.31	10.461%	$117.4311	$117.43	$117.45	$117.40
7 purchase totals =	$546.82		$593.8388	$593.83	$593.85	$593.80