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	$78.89	4.593%	$82.5134	$82.51	$82.50	$82.50
Purchase #2	$111.93	13.519%	$127.0618	$127.06	$127.05	$127.10
Purchase #3	$8.91	5.871%	$9.4331	$9.43	$9.45	$9.40
Purchase #4	$229.85	7.552%	$247.2083	$247.21	$247.20	$247.20
Purchase #5	$36.47	11.128%	$40.5284	$40.53	$40.55	$40.50
Purchase #6	$240.26	6.239%	$255.2498	$255.25	$255.25	$255.20
Purchase #7	$31.33	7.235%	$33.5967	$33.60	$33.60	$33.60
7 purchase totals =	$737.64		$795.5915	$795.59	$795.60	$795.50