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	$133.61	9.399%	$146.168	$146.17	$146.15	$146.20
Purchase #2	$107.65	10.236%	$118.6691	$118.67	$118.65	$118.70
Purchase #3	$78.32	5.253%	$82.4341	$82.43	$82.45	$82.40
Purchase #4	$162.46	12.158%	$182.2119	$182.21	$182.20	$182.20
Purchase #5	$67.95	6.197%	$72.1609	$72.16	$72.15	$72.20
Purchase #6	$11.54	13.412%	$13.0877	$13.09	$13.10	$13.10
Purchase #7	$104.94	7.566%	$112.8798	$112.88	$112.90	$112.90
7 purchase totals =	$666.47		$727.6115	$727.61	$727.60	$727.70