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	$201.97	3.767%	$209.5782	$209.58	$209.60	$209.60
Purchase #2	$133.52	13.342%	$151.3342	$151.33	$151.35	$151.30
Purchase #3	$101.52	5.544%	$107.1483	$107.15	$107.15	$107.10
Purchase #4	$130.59	11.490%	$145.5948	$145.59	$145.60	$145.60
Purchase #5	$145.81	5.535%	$153.8806	$153.88	$153.90	$153.90
Purchase #6	$11.96	7.756%	$12.8876	$12.89	$12.90	$12.90
Purchase #7	$196.66	9.535%	$215.4115	$215.41	$215.40	$215.40
7 purchase totals =	$922.03		$995.8352	$995.83	$995.90	$995.80