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	$93.88	8.555%	$101.9114	$101.91	$101.90	$101.90
Purchase #2	$158.61	9.240%	$173.2656	$173.27	$173.25	$173.30
Purchase #3	$59.98	4.484%	$62.6695	$62.67	$62.65	$62.70
Purchase #4	$176.76	11.103%	$196.3857	$196.39	$196.40	$196.40
Purchase #5	$7.33	7.772%	$7.8997	$7.90	$7.90	$7.90
Purchase #6	$130.45	12.409%	$146.6375	$146.64	$146.65	$146.60
Purchase #7	$50.73	6.177%	$53.8636	$53.86	$53.85	$53.90
7 purchase totals =	$677.74		$742.6330	$742.64	$742.60	$742.70