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	$183.60	11.367%	$204.4698	$204.47	$204.45	$204.50
Purchase #2	$173.65	8.608%	$188.5978	$188.60	$188.60	$188.60
Purchase #3	$33.45	12.229%	$37.5406	$37.54	$37.55	$37.50
Purchase #4	$7.29	4.313%	$7.6044	$7.60	$7.60	$7.60
Purchase #5	$41.67	9.871%	$45.7832	$45.78	$45.80	$45.80
Purchase #6	$173.55	4.865%	$181.9932	$181.99	$182.00	$182.00
Purchase #7	$201.29	11.362%	$224.1606	$224.16	$224.15	$224.20
7 purchase totals =	$814.50		$890.1496	$890.14	$890.15	$890.20