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	$175.32	8.868%	$190.8674	$190.87	$190.85	$190.90
Purchase #2	$205.41	7.654%	$221.1321	$221.13	$221.15	$221.10
Purchase #3	$70.85	10.822%	$78.5174	$78.52	$78.50	$78.50
Purchase #4	$221.57	7.210%	$237.5452	$237.55	$237.55	$237.50
Purchase #5	$54.66	3.497%	$56.5715	$56.57	$56.55	$56.60
Purchase #6	$220.71	9.608%	$241.9158	$241.92	$241.90	$241.90
Purchase #7	$209.56	3.102%	$216.0606	$216.06	$216.05	$216.10
7 purchase totals =	$1,158.08		$1,242.6100	$1,242.62	$1,242.55	$1,242.60