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	$217.62	10.459%	$240.3809	$240.38	$240.40	$240.40
Purchase #2	$188.50	10.822%	$208.8995	$208.90	$208.90	$208.90
Purchase #3	$98.95	12.794%	$111.6097	$111.61	$111.60	$111.60
Purchase #4	$228.81	11.189%	$254.4116	$254.41	$254.40	$254.40
Purchase #5	$97.51	8.273%	$105.577	$105.58	$105.60	$105.60
Purchase #6	$23.59	6.126%	$25.0351	$25.04	$25.05	$25.00
Purchase #7	$246.33	5.466%	$259.7944	$259.79	$259.80	$259.80
7 purchase totals =	$1,101.31		$1,205.7082	$1,205.71	$1,205.75	$1,205.70