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	$96.87	9.202%	$105.784	$105.78	$105.80	$105.80
Purchase #2	$150.30	6.819%	$160.549	$160.55	$160.55	$160.50
Purchase #3	$103.71	7.551%	$111.5411	$111.54	$111.55	$111.50
Purchase #4	$16.68	8.579%	$18.111	$18.11	$18.10	$18.10
Purchase #5	$235.94	6.482%	$251.2336	$251.23	$251.25	$251.20
Purchase #6	$159.88	9.268%	$174.6977	$174.70	$174.70	$174.70
Purchase #7	$207.43	10.131%	$228.4447	$228.44	$228.45	$228.40
7 purchase totals =	$970.81		$1,050.3611	$1,050.35	$1,050.40	$1,050.20