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	$179.52	6.164%	$190.5856	$190.59	$190.60	$190.60
Purchase #2	$176.82	11.265%	$196.7388	$196.74	$196.75	$196.70
Purchase #3	$118.25	5.183%	$124.3789	$124.38	$124.40	$124.40
Purchase #4	$188.56	5.221%	$198.4047	$198.40	$198.40	$198.40
Purchase #5	$132.33	13.532%	$150.2369	$150.24	$150.25	$150.20
Purchase #6	$30.82	12.667%	$34.724	$34.72	$34.70	$34.70
Purchase #7	$136.54	12.466%	$153.5611	$153.56	$153.55	$153.60
7 purchase totals =	$962.84		$1,048.6300	$1,048.63	$1,048.65	$1,048.60