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	$118.61	10.648%	$131.2396	$131.24	$131.25	$131.20
Purchase #2	$60.47	11.831%	$67.6242	$67.62	$67.60	$67.60
Purchase #3	$26.33	5.277%	$27.7194	$27.72	$27.70	$27.70
Purchase #4	$179.38	10.592%	$198.3799	$198.38	$198.40	$198.40
Purchase #5	$50.99	5.465%	$53.7766	$53.78	$53.80	$53.80
Purchase #6	$116.89	5.385%	$123.1845	$123.18	$123.20	$123.20
Purchase #7	$59.42	9.659%	$65.1594	$65.16	$65.15	$65.20
7 purchase totals =	$612.09		$667.0836	$667.08	$667.10	$667.10