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	$162.37	13.109%	$183.6551	$183.66	$183.65	$183.70
Purchase #2	$14.50	7.525%	$15.5911	$15.59	$15.60	$15.60
Purchase #3	$133.80	3.656%	$138.6917	$138.69	$138.70	$138.70
Purchase #4	$243.83	8.769%	$265.2115	$265.21	$265.20	$265.20
Purchase #5	$133.50	5.199%	$140.4407	$140.44	$140.45	$140.40
Purchase #6	$173.40	13.307%	$196.4743	$196.47	$196.45	$196.50
Purchase #7	$234.38	9.265%	$256.0953	$256.10	$256.10	$256.10
7 purchase totals =	$1,095.78		$1,196.1597	$1,196.16	$1,196.15	$1,196.20