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	$66.70	9.521%	$73.0505	$73.05	$73.05	$73.10
Purchase #2	$67.55	6.741%	$72.1035	$72.10	$72.10	$72.10
Purchase #3	$5.71	6.509%	$6.0817	$6.08	$6.10	$6.10
Purchase #4	$147.53	7.439%	$158.5048	$158.50	$158.50	$158.50
Purchase #5	$52.42	10.102%	$57.7155	$57.72	$57.70	$57.70
Purchase #6	$98.41	6.730%	$105.033	$105.03	$105.05	$105.00
Purchase #7	$36.56	9.243%	$39.9392	$39.94	$39.95	$39.90
7 purchase totals =	$474.88		$512.4282	$512.42	$512.45	$512.40