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	$23.34	9.737%	$25.6126	$25.61	$25.60	$25.60
Purchase #2	$198.81	11.347%	$221.369	$221.37	$221.35	$221.40
Purchase #3	$230.37	9.742%	$252.8126	$252.81	$252.80	$252.80
Purchase #4	$147.31	13.595%	$167.3368	$167.34	$167.35	$167.30
Purchase #5	$90.78	13.785%	$103.294	$103.29	$103.30	$103.30
Purchase #6	$100.92	10.579%	$111.5963	$111.60	$111.60	$111.60
Purchase #7	$215.32	4.195%	$224.3527	$224.35	$224.35	$224.40
7 purchase totals =	$1,006.85		$1,106.3740	$1,106.37	$1,106.35	$1,106.40