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	$52.76	12.693%	$59.4568	$59.46	$59.45	$59.50
Purchase #2	$66.25	9.687%	$72.6676	$72.67	$72.65	$72.70
Purchase #3	$114.42	12.727%	$128.9822	$128.98	$129.00	$129.00
Purchase #4	$191.42	7.400%	$205.5851	$205.59	$205.60	$205.60
Purchase #5	$184.51	4.440%	$192.7022	$192.70	$192.70	$192.70
Purchase #6	$224.49	7.624%	$241.6051	$241.61	$241.60	$241.60
Purchase #7	$182.90	4.849%	$191.7688	$191.77	$191.75	$191.80
7 purchase totals =	$1,016.75		$1,092.7678	$1,092.78	$1,092.75	$1,092.90