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	$65.42	13.134%	$74.0123	$74.01	$74.00	$74.00
Purchase #2	$236.71	5.534%	$249.8095	$249.81	$249.80	$249.80
Purchase #3	$41.71	10.435%	$46.0624	$46.06	$46.05	$46.10
Purchase #4	$102.93	8.349%	$111.5236	$111.52	$111.50	$111.50
Purchase #5	$132.28	13.494%	$150.1299	$150.13	$150.15	$150.10
Purchase #6	$16.36	5.533%	$17.2652	$17.27	$17.25	$17.30
Purchase #7	$127.86	6.693%	$136.4177	$136.42	$136.40	$136.40
7 purchase totals =	$723.27		$785.2206	$785.22	$785.15	$785.20