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	$60.80	7.140%	$65.1411	$65.14	$65.15	$65.10
Purchase #2	$186.85	9.758%	$205.0828	$205.08	$205.10	$205.10
Purchase #3	$222.66	10.181%	$245.329	$245.33	$245.35	$245.30
Purchase #4	$157.60	6.141%	$167.2782	$167.28	$167.30	$167.30
Purchase #5	$47.89	10.709%	$53.0185	$53.02	$53.00	$53.00
Purchase #6	$61.72	4.534%	$64.5184	$64.52	$64.50	$64.50
Purchase #7	$201.30	5.634%	$212.6412	$212.64	$212.65	$212.60
7 purchase totals =	$938.82		$1,013.0092	$1,013.01	$1,013.05	$1,012.90