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	$104.70	11.105%	$116.3269	$116.33	$116.35	$116.30
Purchase #2	$82.70	6.449%	$88.0333	$88.03	$88.05	$88.00
Purchase #3	$144.46	4.233%	$150.575	$150.58	$150.60	$150.60
Purchase #4	$33.73	9.702%	$37.0025	$37.00	$37.00	$37.00
Purchase #5	$182.87	5.611%	$193.1308	$193.13	$193.15	$193.10
Purchase #6	$43.69	4.786%	$45.781	$45.78	$45.80	$45.80
Purchase #7	$227.64	4.319%	$237.4718	$237.47	$237.45	$237.50
7 purchase totals =	$819.79		$868.3213	$868.32	$868.40	$868.30