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	$153.49	5.565%	$162.0317	$162.03	$162.05	$162.00
Purchase #2	$137.85	3.307%	$142.4087	$142.41	$142.40	$142.40
Purchase #3	$26.28	12.849%	$29.6567	$29.66	$29.65	$29.70
Purchase #4	$62.69	5.649%	$66.2314	$66.23	$66.25	$66.20
Purchase #5	$131.86	5.399%	$138.9791	$138.98	$139.00	$139.00
Purchase #6	$36.33	10.434%	$40.1207	$40.12	$40.10	$40.10
Purchase #7	$42.72	3.127%	$44.0559	$44.06	$44.05	$44.10
7 purchase totals =	$591.22		$623.4842	$623.49	$623.50	$623.50