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	$67.25	6.558%	$71.6603	$71.66	$71.65	$71.70
Purchase #2	$57.85	7.854%	$62.3935	$62.39	$62.40	$62.40
Purchase #3	$6.28	3.545%	$6.5026	$6.50	$6.50	$6.50
Purchase #4	$54.29	10.784%	$60.1446	$60.14	$60.15	$60.10
Purchase #5	$240.26	7.523%	$258.3348	$258.33	$258.35	$258.30
Purchase #6	$79.38	13.462%	$90.0661	$90.07	$90.05	$90.10
Purchase #7	$232.92	13.109%	$263.4535	$263.45	$263.45	$263.50
7 purchase totals =	$738.23		$812.5554	$812.54	$812.55	$812.60