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	$143.33	13.390%	$162.5219	$162.52	$162.50	$162.50
Purchase #2	$95.87	8.733%	$104.2423	$104.24	$104.25	$104.20
Purchase #3	$218.60	7.763%	$235.5699	$235.57	$235.55	$235.60
Purchase #4	$51.89	4.783%	$54.3719	$54.37	$54.35	$54.40
Purchase #5	$249.50	6.373%	$265.4006	$265.40	$265.40	$265.40
Purchase #6	$219.87	10.322%	$242.565	$242.57	$242.55	$242.60
Purchase #7	$77.42	10.715%	$85.7156	$85.72	$85.70	$85.70
7 purchase totals =	$1,056.48		$1,150.3872	$1,150.39	$1,150.30	$1,150.40