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	$58.48	10.652%	$64.7093	$64.71	$64.70	$64.70
Purchase #2	$20.82	3.667%	$21.5835	$21.58	$21.60	$21.60
Purchase #3	$135.53	12.444%	$152.3954	$152.40	$152.40	$152.40
Purchase #4	$104.43	13.804%	$118.8455	$118.85	$118.85	$118.80
Purchase #5	$10.83	12.815%	$12.2179	$12.22	$12.20	$12.20
Purchase #6	$166.29	3.789%	$172.5907	$172.59	$172.60	$172.60
Purchase #7	$207.93	7.106%	$222.7055	$222.71	$222.70	$222.70
7 purchase totals =	$704.31		$765.0478	$765.06	$765.05	$765.00