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	$142.30	11.699%	$158.9477	$158.95	$158.95	$158.90
Purchase #2	$177.91	7.121%	$190.579	$190.58	$190.60	$190.60
Purchase #3	$68.88	7.614%	$74.1245	$74.12	$74.10	$74.10
Purchase #4	$141.39	8.314%	$153.1452	$153.15	$153.15	$153.10
Purchase #5	$77.42	7.800%	$83.4588	$83.46	$83.45	$83.50
Purchase #6	$72.71	5.281%	$76.5498	$76.55	$76.55	$76.50
Purchase #7	$154.49	11.805%	$172.7275	$172.73	$172.75	$172.70
7 purchase totals =	$835.10		$909.5325	$909.54	$909.55	$909.40