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	$149.50	10.743%	$165.5608	$165.56	$165.55	$165.60
Purchase #2	$243.89	9.602%	$267.3083	$267.31	$267.30	$267.30
Purchase #3	$230.89	3.826%	$239.7239	$239.72	$239.70	$239.70
Purchase #4	$75.53	7.779%	$81.4055	$81.41	$81.40	$81.40
Purchase #5	$145.95	8.262%	$158.0084	$158.01	$158.00	$158.00
Purchase #6	$146.54	5.684%	$154.8693	$154.87	$154.85	$154.90
Purchase #7	$40.86	11.424%	$45.5278	$45.53	$45.55	$45.50
7 purchase totals =	$1,033.16		$1,112.4040	$1,112.41	$1,112.35	$1,112.40