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	$103.40	8.203%	$111.8819	$111.88	$111.90	$111.90
Purchase #2	$12.26	4.186%	$12.7732	$12.77	$12.75	$12.80
Purchase #3	$162.58	10.735%	$180.033	$180.03	$180.05	$180.00
Purchase #4	$112.96	6.858%	$120.7068	$120.71	$120.70	$120.70
Purchase #5	$204.75	9.241%	$223.6709	$223.67	$223.65	$223.70
Purchase #6	$132.59	6.295%	$140.9365	$140.94	$140.95	$140.90
Purchase #7	$168.45	10.150%	$185.5477	$185.55	$185.55	$185.50
7 purchase totals =	$896.99		$975.5500	$975.55	$975.55	$975.50