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	$236.29	13.454%	$268.0805	$268.08	$268.10	$268.10
Purchase #2	$5.36	3.874%	$5.5676	$5.57	$5.55	$5.60
Purchase #3	$145.91	5.726%	$154.2648	$154.26	$154.25	$154.30
Purchase #4	$122.45	4.429%	$127.8733	$127.87	$127.85	$127.90
Purchase #5	$102.73	8.564%	$111.5278	$111.53	$111.55	$111.50
Purchase #6	$31.56	5.582%	$33.3217	$33.32	$33.30	$33.30
Purchase #7	$212.84	12.870%	$240.2325	$240.23	$240.25	$240.20
7 purchase totals =	$857.14		$940.8682	$940.86	$940.85	$940.90