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	$107.42	9.295%	$117.4047	$117.40	$117.40	$117.40
Purchase #2	$167.39	9.103%	$182.6275	$182.63	$182.65	$182.60
Purchase #3	$202.81	13.706%	$230.6071	$230.61	$230.60	$230.60
Purchase #4	$204.66	8.674%	$222.4122	$222.41	$222.40	$222.40
Purchase #5	$130.41	12.591%	$146.8299	$146.83	$146.85	$146.80
Purchase #6	$128.69	7.196%	$137.9505	$137.95	$137.95	$138.00
Purchase #7	$82.43	10.230%	$90.8626	$90.86	$90.85	$90.90
7 purchase totals =	$1,023.81		$1,128.6945	$1,128.69	$1,128.70	$1,128.70