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	$92.59	12.389%	$104.061	$104.06	$104.05	$104.10
Purchase #2	$99.78	4.664%	$104.4337	$104.43	$104.45	$104.40
Purchase #3	$53.39	9.373%	$58.3942	$58.39	$58.40	$58.40
Purchase #4	$235.89	11.175%	$262.2507	$262.25	$262.25	$262.30
Purchase #5	$161.90	4.149%	$168.6172	$168.62	$168.60	$168.60
Purchase #6	$59.30	9.146%	$64.7236	$64.72	$64.70	$64.70
Purchase #7	$242.60	10.746%	$268.6698	$268.67	$268.65	$268.70
7 purchase totals =	$945.45		$1,031.1502	$1,031.14	$1,031.10	$1,031.20