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	$156.88	6.858%	$167.6388	$167.64	$167.65	$167.60
Purchase #2	$170.77	4.409%	$178.2992	$178.30	$178.30	$178.30
Purchase #3	$173.29	5.760%	$183.2715	$183.27	$183.25	$183.30
Purchase #4	$11.45	7.324%	$12.2886	$12.29	$12.30	$12.30
Purchase #5	$79.91	13.234%	$90.4853	$90.49	$90.50	$90.50
Purchase #6	$151.44	5.761%	$160.1645	$160.16	$160.15	$160.20
Purchase #7	$126.79	4.823%	$132.9051	$132.91	$132.90	$132.90
7 purchase totals =	$870.53		$925.0530	$925.06	$925.05	$925.10