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	$121.67	3.409%	$125.8177	$125.82	$125.80	$125.80
Purchase #2	$33.93	13.371%	$38.4668	$38.47	$38.45	$38.50
Purchase #3	$180.59	5.437%	$190.4087	$190.41	$190.40	$190.40
Purchase #4	$176.65	11.189%	$196.4154	$196.42	$196.40	$196.40
Purchase #5	$188.32	5.443%	$198.5703	$198.57	$198.55	$198.60
Purchase #6	$9.58	3.120%	$9.8789	$9.88	$9.90	$9.90
Purchase #7	$27.43	5.450%	$28.9249	$28.92	$28.90	$28.90
7 purchase totals =	$738.17		$788.4827	$788.49	$788.40	$788.50