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	$103.25	13.285%	$116.9668	$116.97	$116.95	$117.00
Purchase #2	$74.56	4.139%	$77.646	$77.65	$77.65	$77.60
Purchase #3	$206.47	4.549%	$215.8623	$215.86	$215.85	$215.90
Purchase #4	$37.31	5.635%	$39.4124	$39.41	$39.40	$39.40
Purchase #5	$15.46	6.268%	$16.429	$16.43	$16.45	$16.40
Purchase #6	$146.85	9.561%	$160.8903	$160.89	$160.90	$160.90
Purchase #7	$125.88	10.610%	$139.2359	$139.24	$139.25	$139.20
7 purchase totals =	$709.78		$766.4427	$766.45	$766.45	$766.40