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	$183.74	9.671%	$201.5095	$201.51	$201.50	$201.50
Purchase #2	$19.68	3.667%	$20.4017	$20.40	$20.40	$20.40
Purchase #3	$16.49	12.678%	$18.5806	$18.58	$18.60	$18.60
Purchase #4	$241.25	12.352%	$271.0492	$271.05	$271.05	$271.00
Purchase #5	$119.85	7.173%	$128.4468	$128.45	$128.45	$128.40
Purchase #6	$150.89	3.776%	$156.5876	$156.59	$156.60	$156.60
Purchase #7	$181.76	13.304%	$205.9414	$205.94	$205.95	$205.90
7 purchase totals =	$913.66		$1,002.5168	$1,002.52	$1,002.55	$1,002.40