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	$69.61	9.861%	$76.4742	$76.47	$76.45	$76.50
Purchase #2	$80.44	3.751%	$83.4573	$83.46	$83.45	$83.50
Purchase #3	$230.35	11.278%	$256.3289	$256.33	$256.35	$256.30
Purchase #4	$34.88	8.673%	$37.9051	$37.91	$37.90	$37.90
Purchase #5	$32.56	10.720%	$36.0504	$36.05	$36.05	$36.10
Purchase #6	$153.52	12.412%	$172.5749	$172.57	$172.55	$172.60
Purchase #7	$75.91	7.415%	$81.5387	$81.54	$81.55	$81.50
7 purchase totals =	$677.27		$744.3295	$744.33	$744.30	$744.40