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	$214.31	13.352%	$242.9247	$242.92	$242.90	$242.90
Purchase #2	$114.81	5.415%	$121.027	$121.03	$121.05	$121.00
Purchase #3	$162.35	10.514%	$179.4195	$179.42	$179.40	$179.40
Purchase #4	$151.67	13.697%	$172.4442	$172.44	$172.45	$172.40
Purchase #5	$17.64	5.646%	$18.636	$18.64	$18.65	$18.60
Purchase #6	$177.88	10.465%	$196.4951	$196.50	$196.50	$196.50
Purchase #7	$73.59	12.693%	$82.9308	$82.93	$82.95	$82.90
7 purchase totals =	$912.25		$1,013.8773	$1,013.88	$1,013.90	$1,013.70