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	$62.51	4.549%	$65.3536	$65.35	$65.35	$65.40
Purchase #2	$189.57	4.487%	$198.076	$198.08	$198.10	$198.10
Purchase #3	$135.65	7.461%	$145.7708	$145.77	$145.75	$145.80
Purchase #4	$101.40	3.403%	$104.8506	$104.85	$104.85	$104.90
Purchase #5	$104.54	7.367%	$112.2415	$112.24	$112.25	$112.20
Purchase #6	$131.47	8.471%	$142.6068	$142.61	$142.60	$142.60
Purchase #7	$43.32	4.576%	$45.3023	$45.30	$45.30	$45.30
7 purchase totals =	$768.46		$814.2016	$814.20	$814.20	$814.30