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	$47.76	11.661%	$53.3293	$53.33	$53.35	$53.30
Purchase #2	$161.98	8.754%	$176.1597	$176.16	$176.15	$176.20
Purchase #3	$226.64	10.476%	$250.3828	$250.38	$250.40	$250.40
Purchase #4	$18.95	6.284%	$20.1408	$20.14	$20.15	$20.10
Purchase #5	$213.49	11.725%	$238.5217	$238.52	$238.50	$238.50
Purchase #6	$182.51	9.461%	$199.7773	$199.78	$199.80	$199.80
Purchase #7	$218.28	4.602%	$228.3252	$228.33	$228.35	$228.30
7 purchase totals =	$1,069.61		$1,166.6368	$1,166.64	$1,166.70	$1,166.60