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	$142.33	6.461%	$151.5259	$151.53	$151.55	$151.50
Purchase #2	$72.75	13.813%	$82.799	$82.80	$82.80	$82.80
Purchase #3	$155.65	13.408%	$176.5196	$176.52	$176.50	$176.50
Purchase #4	$108.32	3.425%	$112.03	$112.03	$112.05	$112.00
Purchase #5	$136.84	10.664%	$151.4326	$151.43	$151.45	$151.40
Purchase #6	$139.32	12.406%	$156.604	$156.60	$156.60	$156.60
Purchase #7	$180.70	9.719%	$198.2622	$198.26	$198.25	$198.30
7 purchase totals =	$935.91		$1,029.1733	$1,029.17	$1,029.20	$1,029.10