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	$149.84	9.853%	$164.6037	$164.60	$164.60	$164.60
Purchase #2	$31.95	8.413%	$34.638	$34.64	$34.65	$34.60
Purchase #3	$241.72	8.647%	$262.6215	$262.62	$262.60	$262.60
Purchase #4	$93.33	12.666%	$105.1512	$105.15	$105.15	$105.20
Purchase #5	$175.52	6.689%	$187.2605	$187.26	$187.25	$187.30
Purchase #6	$106.50	7.593%	$114.5865	$114.59	$114.60	$114.60
Purchase #7	$103.83	8.242%	$112.3877	$112.39	$112.40	$112.40
7 purchase totals =	$902.69		$981.2491	$981.25	$981.25	$981.30