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	$185.29	5.803%	$196.0424	$196.04	$196.05	$196.00
Purchase #2	$59.75	11.326%	$66.5173	$66.52	$66.50	$66.50
Purchase #3	$185.48	5.809%	$196.2545	$196.25	$196.25	$196.30
Purchase #4	$113.68	4.314%	$118.5842	$118.58	$118.60	$118.60
Purchase #5	$153.90	7.656%	$165.6826	$165.68	$165.70	$165.70
Purchase #6	$87.84	9.735%	$96.3912	$96.39	$96.40	$96.40
Purchase #7	$18.67	8.209%	$20.2026	$20.20	$20.20	$20.20
7 purchase totals =	$804.61		$859.6748	$859.66	$859.70	$859.70