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	$52.37	13.565%	$59.474	$59.47	$59.45	$59.50
Purchase #2	$244.39	9.203%	$266.8812	$266.88	$266.90	$266.90
Purchase #3	$247.87	3.304%	$256.0596	$256.06	$256.05	$256.10
Purchase #4	$71.84	11.185%	$79.8753	$79.88	$79.90	$79.90
Purchase #5	$138.74	12.182%	$155.6413	$155.64	$155.65	$155.60
Purchase #6	$213.72	3.219%	$220.5996	$220.60	$220.60	$220.60
Purchase #7	$7.38	3.491%	$7.6376	$7.64	$7.65	$7.60
7 purchase totals =	$976.31		$1,046.1686	$1,046.17	$1,046.20	$1,046.20