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	$54.29	4.592%	$56.783	$56.78	$56.80	$56.80
Purchase #2	$74.61	4.835%	$78.2174	$78.22	$78.20	$78.20
Purchase #3	$59.87	12.451%	$67.3244	$67.32	$67.30	$67.30
Purchase #4	$29.55	11.126%	$32.8377	$32.84	$32.85	$32.80
Purchase #5	$85.59	9.376%	$93.6149	$93.61	$93.60	$93.60
Purchase #6	$247.67	4.333%	$258.4015	$258.40	$258.40	$258.40
Purchase #7	$127.44	5.829%	$134.8685	$134.87	$134.85	$134.90
7 purchase totals =	$679.02		$722.0474	$722.04	$722.00	$722.00