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	$95.90	8.554%	$104.1033	$104.10	$104.10	$104.10
Purchase #2	$145.48	6.817%	$155.3974	$155.40	$155.40	$155.40
Purchase #3	$172.88	9.664%	$189.5871	$189.59	$189.60	$189.60
Purchase #4	$95.73	8.522%	$103.8881	$103.89	$103.90	$103.90
Purchase #5	$206.31	4.563%	$215.7239	$215.72	$215.70	$215.70
Purchase #6	$140.72	10.393%	$155.345	$155.35	$155.35	$155.30
Purchase #7	$105.89	3.343%	$109.4299	$109.43	$109.45	$109.40
7 purchase totals =	$962.91		$1,033.4747	$1,033.48	$1,033.50	$1,033.40