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	$14.82	11.443%	$16.5159	$16.52	$16.50	$16.50
Purchase #2	$155.40	11.560%	$173.3642	$173.36	$173.35	$173.40
Purchase #3	$111.57	6.270%	$118.5654	$118.57	$118.55	$118.60
Purchase #4	$49.72	10.307%	$54.8446	$54.84	$54.85	$54.80
Purchase #5	$219.32	4.686%	$229.5973	$229.60	$229.60	$229.60
Purchase #6	$141.27	5.372%	$148.859	$148.86	$148.85	$148.90
Purchase #7	$43.87	4.488%	$45.8389	$45.84	$45.85	$45.80
7 purchase totals =	$735.97		$787.5853	$787.59	$787.55	$787.60