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	$28.65	12.767%	$32.3077	$32.31	$32.30	$32.30
Purchase #2	$198.28	4.382%	$206.9686	$206.97	$206.95	$207.00
Purchase #3	$60.96	10.334%	$67.2596	$67.26	$67.25	$67.30
Purchase #4	$7.52	5.494%	$7.9331	$7.93	$7.95	$7.90
Purchase #5	$103.89	7.792%	$111.9851	$111.99	$112.00	$112.00
Purchase #6	$31.44	6.230%	$33.3987	$33.40	$33.40	$33.40
Purchase #7	$12.76	13.743%	$14.5136	$14.51	$14.50	$14.50
7 purchase totals =	$443.50		$474.3664	$474.37	$474.35	$474.40