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	$64.26	5.551%	$67.8271	$67.83	$67.85	$67.80
Purchase #2	$128.40	3.339%	$132.6873	$132.69	$132.70	$132.70
Purchase #3	$195.47	4.242%	$203.7618	$203.76	$203.75	$203.80
Purchase #4	$138.93	9.588%	$152.2506	$152.25	$152.25	$152.30
Purchase #5	$38.93	4.760%	$40.7831	$40.78	$40.80	$40.80
Purchase #6	$217.38	7.673%	$234.0596	$234.06	$234.05	$234.10
Purchase #7	$229.78	11.596%	$256.4253	$256.43	$256.45	$256.40
7 purchase totals =	$1,013.15		$1,087.7948	$1,087.80	$1,087.85	$1,087.90