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	$231.36	7.602%	$248.948	$248.95	$248.95	$248.90
Purchase #2	$246.90	9.114%	$269.4025	$269.40	$269.40	$269.40
Purchase #3	$138.92	13.859%	$158.1729	$158.17	$158.15	$158.20
Purchase #4	$29.92	8.640%	$32.5051	$32.51	$32.50	$32.50
Purchase #5	$40.86	12.237%	$45.86	$45.86	$45.85	$45.90
Purchase #6	$127.66	10.310%	$140.8217	$140.82	$140.80	$140.80
Purchase #7	$114.97	6.867%	$122.865	$122.87	$122.85	$122.90
7 purchase totals =	$930.59		$1,018.5752	$1,018.58	$1,018.50	$1,018.60