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	$158.80	9.352%	$173.651	$173.65	$173.65	$173.70
Purchase #2	$50.51	12.404%	$56.7753	$56.78	$56.80	$56.80
Purchase #3	$131.84	8.151%	$142.5863	$142.59	$142.60	$142.60
Purchase #4	$30.58	3.305%	$31.5907	$31.59	$31.60	$31.60
Purchase #5	$164.33	3.138%	$169.4867	$169.49	$169.50	$169.50
Purchase #6	$169.41	7.400%	$181.9463	$181.95	$181.95	$181.90
Purchase #7	$18.87	10.595%	$20.8693	$20.87	$20.85	$20.90
7 purchase totals =	$724.34		$776.9056	$776.92	$776.95	$777.00