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	$97.64	7.782%	$105.2383	$105.24	$105.25	$105.20
Purchase #2	$75.94	9.172%	$82.9052	$82.91	$82.90	$82.90
Purchase #3	$19.71	4.160%	$20.5299	$20.53	$20.55	$20.50
Purchase #4	$105.38	8.759%	$114.6102	$114.61	$114.60	$114.60
Purchase #5	$107.51	5.634%	$113.5671	$113.57	$113.55	$113.60
Purchase #6	$198.34	4.827%	$207.9139	$207.91	$207.90	$207.90
Purchase #7	$67.99	5.528%	$71.7485	$71.75	$71.75	$71.70
7 purchase totals =	$672.51		$716.5131	$716.52	$716.50	$716.40