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	$111.75	13.339%	$126.6563	$126.66	$126.65	$126.70
Purchase #2	$28.74	13.322%	$32.5687	$32.57	$32.55	$32.60
Purchase #3	$77.31	13.146%	$87.4732	$87.47	$87.45	$87.50
Purchase #4	$134.95	9.416%	$147.6569	$147.66	$147.65	$147.70
Purchase #5	$51.72	7.260%	$55.4749	$55.47	$55.45	$55.50
Purchase #6	$142.39	8.786%	$154.9004	$154.90	$154.90	$154.90
Purchase #7	$187.31	7.103%	$200.6146	$200.61	$200.60	$200.60
7 purchase totals =	$734.17		$805.3450	$805.34	$805.25	$805.50