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	$248.72	4.456%	$259.803	$259.80	$259.80	$259.80
Purchase #2	$124.34	8.530%	$134.9462	$134.95	$134.95	$134.90
Purchase #3	$228.63	13.253%	$258.9303	$258.93	$258.95	$258.90
Purchase #4	$95.43	5.191%	$100.3838	$100.38	$100.40	$100.40
Purchase #5	$95.67	10.381%	$105.6015	$105.60	$105.60	$105.60
Purchase #6	$186.36	4.743%	$195.1991	$195.20	$195.20	$195.20
Purchase #7	$38.31	9.801%	$42.0648	$42.06	$42.05	$42.10
7 purchase totals =	$1,017.46		$1,096.9287	$1,096.92	$1,096.95	$1,096.90