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	$158.38	5.756%	$167.4964	$167.50	$167.50	$167.50
Purchase #2	$95.42	13.625%	$108.421	$108.42	$108.40	$108.40
Purchase #3	$134.70	8.765%	$146.5065	$146.51	$146.50	$146.50
Purchase #4	$141.61	9.858%	$155.5699	$155.57	$155.55	$155.60
Purchase #5	$196.70	12.510%	$221.3072	$221.31	$221.30	$221.30
Purchase #6	$74.38	11.615%	$83.0192	$83.02	$83.00	$83.00
Purchase #7	$175.83	4.297%	$183.3854	$183.39	$183.40	$183.40
7 purchase totals =	$977.02		$1,065.7056	$1,065.72	$1,065.65	$1,065.70