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	$96.47	11.258%	$107.3306	$107.33	$107.35	$107.30
Purchase #2	$161.77	12.380%	$181.7971	$181.80	$181.80	$181.80
Purchase #3	$137.90	8.427%	$149.5208	$149.52	$149.50	$149.50
Purchase #4	$142.54	4.305%	$148.6763	$148.68	$148.70	$148.70
Purchase #5	$240.53	7.205%	$257.8602	$257.86	$257.85	$257.90
Purchase #6	$154.50	11.724%	$172.6136	$172.61	$172.60	$172.60
Purchase #7	$173.50	13.270%	$196.5235	$196.52	$196.50	$196.50
7 purchase totals =	$1,107.21		$1,214.3221	$1,214.32	$1,214.30	$1,214.30