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	$204.92	4.562%	$214.2685	$214.27	$214.25	$214.30
Purchase #2	$132.81	13.284%	$150.4525	$150.45	$150.45	$150.50
Purchase #3	$247.59	4.126%	$257.8056	$257.81	$257.80	$257.80
Purchase #4	$181.47	8.404%	$196.7207	$196.72	$196.70	$196.70
Purchase #5	$216.51	11.298%	$240.9713	$240.97	$240.95	$241.00
Purchase #6	$59.79	4.551%	$62.511	$62.51	$62.50	$62.50
Purchase #7	$26.34	8.596%	$28.6042	$28.60	$28.60	$28.60
7 purchase totals =	$1,069.43		$1,151.3338	$1,151.33	$1,151.25	$1,151.40