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	$54.82	13.589%	$62.2695	$62.27	$62.25	$62.30
Purchase #2	$153.61	13.117%	$173.759	$173.76	$173.75	$173.80
Purchase #3	$100.86	4.355%	$105.2525	$105.25	$105.25	$105.30
Purchase #4	$61.31	10.714%	$67.8788	$67.88	$67.90	$67.90
Purchase #5	$249.91	10.698%	$276.6454	$276.65	$276.65	$276.60
Purchase #6	$207.37	8.315%	$224.6128	$224.61	$224.60	$224.60
Purchase #7	$81.70	6.605%	$87.0963	$87.10	$87.10	$87.10
7 purchase totals =	$909.58		$997.5143	$997.52	$997.50	$997.60