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	$138.96	13.637%	$157.91	$157.91	$157.90	$157.90
Purchase #2	$136.55	6.584%	$145.5405	$145.54	$145.55	$145.50
Purchase #3	$42.64	7.145%	$45.6866	$45.69	$45.70	$45.70
Purchase #4	$179.32	4.428%	$187.2603	$187.26	$187.25	$187.30
Purchase #5	$240.25	13.144%	$271.8285	$271.83	$271.85	$271.80
Purchase #6	$46.51	10.480%	$51.3842	$51.38	$51.40	$51.40
Purchase #7	$167.63	10.125%	$184.6025	$184.60	$184.60	$184.60
7 purchase totals =	$951.86		$1,044.2126	$1,044.21	$1,044.25	$1,044.20