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	$182.90	13.759%	$208.0652	$208.07	$208.05	$208.10
Purchase #2	$237.61	13.392%	$269.4307	$269.43	$269.45	$269.40
Purchase #3	$150.32	10.698%	$166.4012	$166.40	$166.40	$166.40
Purchase #4	$47.84	11.186%	$53.1914	$53.19	$53.20	$53.20
Purchase #5	$104.95	4.138%	$109.2928	$109.29	$109.30	$109.30
Purchase #6	$52.45	4.680%	$54.9047	$54.90	$54.90	$54.90
Purchase #7	$108.39	8.424%	$117.5208	$117.52	$117.50	$117.50
7 purchase totals =	$884.46		$978.8068	$978.80	$978.80	$978.80