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	$250.92	4.524%	$262.2716	$262.27	$262.25	$262.30
Purchase #2	$182.25	9.106%	$198.8457	$198.85	$198.85	$198.80
Purchase #3	$246.60	5.169%	$259.3468	$259.35	$259.35	$259.30
Purchase #4	$117.49	8.324%	$127.2699	$127.27	$127.25	$127.30
Purchase #5	$78.58	10.807%	$87.0721	$87.07	$87.05	$87.10
Purchase #6	$119.68	6.350%	$127.2797	$127.28	$127.30	$127.30
Purchase #7	$134.26	12.310%	$150.7874	$150.79	$150.80	$150.80
7 purchase totals =	$1,129.78		$1,212.8732	$1,212.88	$1,212.85	$1,212.90