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	$60.51	8.182%	$65.4609	$65.46	$65.45	$65.50
Purchase #2	$128.65	13.643%	$146.2017	$146.20	$146.20	$146.20
Purchase #3	$168.52	3.736%	$174.8159	$174.82	$174.80	$174.80
Purchase #4	$169.72	5.728%	$179.4416	$179.44	$179.45	$179.40
Purchase #5	$102.46	11.121%	$113.8546	$113.85	$113.85	$113.90
Purchase #6	$101.81	9.791%	$111.7782	$111.78	$111.80	$111.80
Purchase #7	$157.38	3.394%	$162.7215	$162.72	$162.70	$162.70
7 purchase totals =	$889.05		$954.2744	$954.27	$954.25	$954.30