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	$149.55	4.698%	$156.5759	$156.58	$156.60	$156.60
Purchase #2	$40.77	4.170%	$42.4701	$42.47	$42.45	$42.50
Purchase #3	$157.31	6.739%	$167.9111	$167.91	$167.90	$167.90
Purchase #4	$248.92	6.807%	$265.864	$265.86	$265.85	$265.90
Purchase #5	$147.29	3.128%	$151.8972	$151.90	$151.90	$151.90
Purchase #6	$56.43	10.345%	$62.2677	$62.27	$62.25	$62.30
Purchase #7	$146.40	8.153%	$158.336	$158.34	$158.35	$158.30
7 purchase totals =	$946.67		$1,005.3220	$1,005.33	$1,005.30	$1,005.40