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	$241.78	9.506%	$264.7636	$264.76	$264.75	$264.80
Purchase #2	$169.67	11.116%	$188.5305	$188.53	$188.55	$188.50
Purchase #3	$189.40	10.178%	$208.6771	$208.68	$208.70	$208.70
Purchase #4	$98.47	5.204%	$103.5944	$103.59	$103.60	$103.60
Purchase #5	$146.50	7.744%	$157.845	$157.85	$157.85	$157.80
Purchase #6	$111.90	10.155%	$123.2634	$123.26	$123.25	$123.30
Purchase #7	$164.35	10.870%	$182.2148	$182.21	$182.20	$182.20
7 purchase totals =	$1,122.07		$1,228.8888	$1,228.88	$1,228.90	$1,228.90