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	$79.27	9.625%	$86.8997	$86.90	$86.90	$86.90
Purchase #2	$144.59	4.599%	$151.2397	$151.24	$151.25	$151.20
Purchase #3	$89.60	4.717%	$93.8264	$93.83	$93.85	$93.80
Purchase #4	$45.85	5.564%	$48.4011	$48.40	$48.40	$48.40
Purchase #5	$26.50	3.847%	$27.5195	$27.52	$27.50	$27.50
Purchase #6	$17.52	7.637%	$18.858	$18.86	$18.85	$18.90
Purchase #7	$14.69	13.498%	$16.6729	$16.67	$16.65	$16.70
7 purchase totals =	$418.02		$443.4173	$443.42	$443.40	$443.40