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	$164.58	9.221%	$179.7559	$179.76	$179.75	$179.80
Purchase #2	$153.88	11.451%	$171.5008	$171.50	$171.50	$171.50
Purchase #3	$143.99	6.572%	$153.453	$153.45	$153.45	$153.50
Purchase #4	$55.65	12.688%	$62.7109	$62.71	$62.70	$62.70
Purchase #5	$117.48	8.563%	$127.5398	$127.54	$127.55	$127.50
Purchase #6	$50.78	5.607%	$53.6272	$53.63	$53.65	$53.60
Purchase #7	$242.48	6.720%	$258.7747	$258.77	$258.75	$258.80
7 purchase totals =	$928.84		$1,007.3623	$1,007.36	$1,007.35	$1,007.40