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	$147.51	4.332%	$153.9001	$153.90	$153.90	$153.90
Purchase #2	$140.55	7.136%	$150.5796	$150.58	$150.60	$150.60
Purchase #3	$180.52	5.754%	$190.9071	$190.91	$190.90	$190.90
Purchase #4	$99.62	8.504%	$108.0917	$108.09	$108.10	$108.10
Purchase #5	$175.93	10.579%	$194.5416	$194.54	$194.55	$194.50
Purchase #6	$71.78	12.275%	$80.591	$80.59	$80.60	$80.60
Purchase #7	$189.45	13.331%	$214.7056	$214.71	$214.70	$214.70
7 purchase totals =	$1,005.36		$1,093.3167	$1,093.32	$1,093.35	$1,093.30