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	$227.66	13.563%	$258.5375	$258.54	$258.55	$258.50
Purchase #2	$74.39	4.779%	$77.9451	$77.95	$77.95	$77.90
Purchase #3	$176.43	8.503%	$191.4318	$191.43	$191.45	$191.40
Purchase #4	$35.94	3.456%	$37.1821	$37.18	$37.20	$37.20
Purchase #5	$245.30	11.251%	$272.8987	$272.90	$272.90	$272.90
Purchase #6	$10.42	6.402%	$11.0871	$11.09	$11.10	$11.10
Purchase #7	$181.95	10.318%	$200.7236	$200.72	$200.70	$200.70
7 purchase totals =	$952.09		$1,049.8059	$1,049.81	$1,049.85	$1,049.70