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	$166.46	9.258%	$181.8709	$181.87	$181.85	$181.90
Purchase #2	$55.75	6.726%	$59.4997	$59.50	$59.50	$59.50
Purchase #3	$80.97	11.768%	$90.4985	$90.50	$90.50	$90.50
Purchase #4	$63.48	4.416%	$66.2833	$66.28	$66.30	$66.30
Purchase #5	$131.82	10.322%	$145.4265	$145.43	$145.45	$145.40
Purchase #6	$49.45	10.854%	$54.8173	$54.82	$54.80	$54.80
Purchase #7	$11.74	10.635%	$12.9885	$12.99	$13.00	$13.00
7 purchase totals =	$559.67		$611.3847	$611.39	$611.40	$611.40