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	$166.85	8.792%	$181.5195	$181.52	$181.50	$181.50
Purchase #2	$41.54	4.170%	$43.2722	$43.27	$43.25	$43.30
Purchase #3	$51.28	13.326%	$58.1136	$58.11	$58.10	$58.10
Purchase #4	$58.79	11.208%	$65.3792	$65.38	$65.40	$65.40
Purchase #5	$89.99	11.407%	$100.2552	$100.26	$100.25	$100.30
Purchase #6	$12.57	7.679%	$13.5353	$13.54	$13.55	$13.50
Purchase #7	$126.94	7.557%	$136.5329	$136.53	$136.55	$136.50
7 purchase totals =	$547.96		$598.6079	$598.61	$598.60	$598.60