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	$69.38	5.579%	$73.2507	$73.25	$73.25	$73.30
Purchase #2	$247.46	13.720%	$281.4115	$281.41	$281.40	$281.40
Purchase #3	$40.26	12.236%	$45.1862	$45.19	$45.20	$45.20
Purchase #4	$82.61	3.516%	$85.5146	$85.51	$85.50	$85.50
Purchase #5	$54.43	13.590%	$61.827	$61.83	$61.85	$61.80
Purchase #6	$75.58	11.760%	$84.4682	$84.47	$84.45	$84.50
Purchase #7	$200.70	5.105%	$210.9457	$210.95	$210.95	$210.90
7 purchase totals =	$770.42		$842.6039	$842.61	$842.60	$842.60