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	$209.95	11.768%	$234.6569	$234.66	$234.65	$234.70
Purchase #2	$48.64	3.767%	$50.4723	$50.47	$50.45	$50.50
Purchase #3	$22.66	11.123%	$25.1805	$25.18	$25.20	$25.20
Purchase #4	$235.40	11.687%	$262.9112	$262.91	$262.90	$262.90
Purchase #5	$152.37	12.806%	$171.8825	$171.88	$171.90	$171.90
Purchase #6	$146.93	13.203%	$166.3292	$166.33	$166.35	$166.30
Purchase #7	$200.64	13.520%	$227.7665	$227.77	$227.75	$227.80
7 purchase totals =	$1,016.59		$1,139.1991	$1,139.20	$1,139.20	$1,139.30