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	$38.67	11.370%	$43.0668	$43.07	$43.05	$43.10
Purchase #2	$39.37	11.284%	$43.8125	$43.81	$43.80	$43.80
Purchase #3	$129.86	11.431%	$144.7043	$144.70	$144.70	$144.70
Purchase #4	$82.79	3.122%	$85.3747	$85.37	$85.35	$85.40
Purchase #5	$128.68	7.449%	$138.2654	$138.27	$138.25	$138.30
Purchase #6	$41.85	8.136%	$45.2549	$45.25	$45.25	$45.30
Purchase #7	$51.41	5.540%	$54.2581	$54.26	$54.25	$54.30
7 purchase totals =	$512.63		$554.7367	$554.73	$554.65	$554.90