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	$227.36	7.140%	$243.5935	$243.59	$243.60	$243.60
Purchase #2	$239.53	5.620%	$252.9916	$252.99	$253.00	$253.00
Purchase #3	$154.64	4.688%	$161.8895	$161.89	$161.90	$161.90
Purchase #4	$165.89	9.622%	$181.8519	$181.85	$181.85	$181.90
Purchase #5	$122.64	12.186%	$137.5849	$137.58	$137.60	$137.60
Purchase #6	$101.30	5.802%	$107.1774	$107.18	$107.20	$107.20
Purchase #7	$102.65	8.663%	$111.5426	$111.54	$111.55	$111.50
7 purchase totals =	$1,114.01		$1,196.6314	$1,196.62	$1,196.70	$1,196.70