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	$59.73	4.475%	$62.4029	$62.40	$62.40	$62.40
Purchase #2	$144.47	3.167%	$149.0454	$149.05	$149.05	$149.00
Purchase #3	$61.27	9.669%	$67.1942	$67.19	$67.20	$67.20
Purchase #4	$120.55	10.301%	$132.9679	$132.97	$132.95	$133.00
Purchase #5	$84.42	6.408%	$89.8296	$89.83	$89.85	$89.80
Purchase #6	$85.53	5.277%	$90.0434	$90.04	$90.05	$90.00
Purchase #7	$130.82	5.366%	$137.8398	$137.84	$137.85	$137.80
7 purchase totals =	$686.79		$729.3232	$729.32	$729.35	$729.20