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	$167.82	12.386%	$188.6062	$188.61	$188.60	$188.60
Purchase #2	$165.64	7.323%	$177.7698	$177.77	$177.75	$177.80
Purchase #3	$171.28	10.650%	$189.5213	$189.52	$189.50	$189.50
Purchase #4	$60.38	11.111%	$67.0888	$67.09	$67.10	$67.10
Purchase #5	$164.41	5.396%	$173.2816	$173.28	$173.30	$173.30
Purchase #6	$114.55	11.348%	$127.5491	$127.55	$127.55	$127.50
Purchase #7	$78.66	3.138%	$81.1284	$81.13	$81.15	$81.10
7 purchase totals =	$922.74		$1,004.9452	$1,004.95	$1,004.95	$1,004.90