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	$67.96	6.348%	$72.2741	$72.27	$72.25	$72.30
Purchase #2	$77.51	5.467%	$81.7475	$81.75	$81.75	$81.70
Purchase #3	$20.90	9.520%	$22.8897	$22.89	$22.90	$22.90
Purchase #4	$125.54	10.606%	$138.8548	$138.85	$138.85	$138.90
Purchase #5	$9.72	5.341%	$10.2391	$10.24	$10.25	$10.20
Purchase #6	$119.49	12.688%	$134.6509	$134.65	$134.65	$134.70
Purchase #7	$156.78	6.706%	$167.2937	$167.29	$167.30	$167.30
7 purchase totals =	$577.90		$627.9498	$627.94	$627.95	$628.00