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	$144.64	8.489%	$156.9185	$156.92	$156.90	$156.90
Purchase #2	$131.35	12.235%	$147.4207	$147.42	$147.40	$147.40
Purchase #3	$238.33	13.534%	$270.5856	$270.59	$270.60	$270.60
Purchase #4	$194.74	13.514%	$221.0572	$221.06	$221.05	$221.10
Purchase #5	$181.31	3.516%	$187.6849	$187.68	$187.70	$187.70
Purchase #6	$47.61	13.797%	$54.1788	$54.18	$54.20	$54.20
Purchase #7	$61.47	7.379%	$66.0059	$66.01	$66.00	$66.00
7 purchase totals =	$999.45		$1,103.8516	$1,103.86	$1,103.85	$1,103.90