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	$170.35	12.671%	$191.935	$191.94	$191.95	$191.90
Purchase #2	$147.83	13.102%	$167.1987	$167.20	$167.20	$167.20
Purchase #3	$122.83	8.700%	$133.5162	$133.52	$133.50	$133.50
Purchase #4	$173.29	10.477%	$191.4456	$191.45	$191.45	$191.40
Purchase #5	$76.59	6.765%	$81.7713	$81.77	$81.75	$81.80
Purchase #6	$59.57	3.868%	$61.8742	$61.87	$61.85	$61.90
Purchase #7	$147.56	7.296%	$158.326	$158.33	$158.35	$158.30
7 purchase totals =	$898.02		$986.0670	$986.08	$986.05	$986.00