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	$157.32	6.442%	$167.4546	$167.45	$167.45	$167.50
Purchase #2	$75.72	6.395%	$80.5623	$80.56	$80.55	$80.60
Purchase #3	$118.74	10.364%	$131.0462	$131.05	$131.05	$131.00
Purchase #4	$120.77	10.602%	$133.574	$133.57	$133.55	$133.60
Purchase #5	$92.71	9.350%	$101.3784	$101.38	$101.40	$101.40
Purchase #6	$136.85	6.151%	$145.2676	$145.27	$145.25	$145.30
Purchase #7	$50.82	7.869%	$54.819	$54.82	$54.80	$54.80
7 purchase totals =	$752.93		$814.1021	$814.10	$814.05	$814.20