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	$78.38	9.382%	$85.7336	$85.73	$85.75	$85.70
Purchase #2	$133.55	4.305%	$139.2993	$139.30	$139.30	$139.30
Purchase #3	$160.67	11.233%	$178.7181	$178.72	$178.70	$178.70
Purchase #4	$59.44	3.613%	$61.5876	$61.59	$61.60	$61.60
Purchase #5	$136.77	12.332%	$153.6365	$153.64	$153.65	$153.60
Purchase #6	$106.68	4.608%	$111.5958	$111.60	$111.60	$111.60
Purchase #7	$8.33	5.704%	$8.8051	$8.81	$8.80	$8.80
7 purchase totals =	$683.82		$739.3760	$739.39	$739.40	$739.30