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	$73.65	10.461%	$81.3545	$81.35	$81.35	$81.40
Purchase #2	$153.86	12.726%	$173.4402	$173.44	$173.45	$173.40
Purchase #3	$208.33	10.108%	$229.388	$229.39	$229.40	$229.40
Purchase #4	$234.88	11.291%	$261.4003	$261.40	$261.40	$261.40
Purchase #5	$47.46	12.238%	$53.2682	$53.27	$53.25	$53.30
Purchase #6	$8.85	13.396%	$10.0355	$10.04	$10.05	$10.00
Purchase #7	$147.38	4.451%	$153.9399	$153.94	$153.95	$153.90
7 purchase totals =	$874.41		$962.8266	$962.83	$962.85	$962.80