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	$163.60	5.839%	$173.1526	$173.15	$173.15	$173.20
Purchase #2	$117.91	5.391%	$124.2665	$124.27	$124.25	$124.30
Purchase #3	$41.42	5.703%	$43.7822	$43.78	$43.80	$43.80
Purchase #4	$89.88	6.155%	$95.4121	$95.41	$95.40	$95.40
Purchase #5	$56.61	12.710%	$63.8051	$63.81	$63.80	$63.80
Purchase #6	$51.55	4.560%	$53.9007	$53.90	$53.90	$53.90
Purchase #7	$137.30	5.446%	$144.7774	$144.78	$144.80	$144.80
7 purchase totals =	$658.27		$699.0966	$699.10	$699.10	$699.20