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	$187.78	10.651%	$207.7804	$207.78	$207.80	$207.80
Purchase #2	$176.85	11.288%	$196.8128	$196.81	$196.80	$196.80
Purchase #3	$69.47	13.502%	$78.8498	$78.85	$78.85	$78.80
Purchase #4	$40.81	5.162%	$42.9166	$42.92	$42.90	$42.90
Purchase #5	$234.92	9.325%	$256.8263	$256.83	$256.85	$256.80
Purchase #6	$56.41	11.817%	$63.076	$63.08	$63.10	$63.10
Purchase #7	$157.93	6.140%	$167.6269	$167.63	$167.65	$167.60
7 purchase totals =	$924.17		$1,013.8888	$1,013.90	$1,013.95	$1,013.80