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	$22.60	9.569%	$24.7626	$24.76	$24.75	$24.80
Purchase #2	$84.68	7.751%	$91.2435	$91.24	$91.25	$91.20
Purchase #3	$183.28	7.195%	$196.467	$196.47	$196.45	$196.50
Purchase #4	$73.52	11.605%	$82.052	$82.05	$82.05	$82.10
Purchase #5	$68.88	10.867%	$76.3652	$76.37	$76.35	$76.40
Purchase #6	$197.42	4.767%	$206.831	$206.83	$206.85	$206.80
Purchase #7	$90.91	9.160%	$99.2374	$99.24	$99.25	$99.20
7 purchase totals =	$721.29		$776.9587	$776.96	$776.95	$777.00