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	$45.98	5.836%	$48.6634	$48.66	$48.65	$48.70
Purchase #2	$74.60	5.388%	$78.6194	$78.62	$78.60	$78.60
Purchase #3	$67.72	12.855%	$76.4254	$76.43	$76.45	$76.40
Purchase #4	$218.93	6.570%	$233.3137	$233.31	$233.30	$233.30
Purchase #5	$96.36	3.545%	$99.776	$99.78	$99.80	$99.80
Purchase #6	$113.85	6.105%	$120.8005	$120.80	$120.80	$120.80
Purchase #7	$226.39	10.806%	$250.8537	$250.85	$250.85	$250.90
7 purchase totals =	$843.83		$908.4521	$908.45	$908.45	$908.50