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	$182.53	9.179%	$199.2844	$199.28	$199.30	$199.30
Purchase #2	$118.34	10.593%	$130.8758	$130.88	$130.90	$130.90
Purchase #3	$231.59	10.291%	$255.4229	$255.42	$255.40	$255.40
Purchase #4	$50.53	8.137%	$54.6416	$54.64	$54.65	$54.60
Purchase #5	$135.32	5.308%	$142.5028	$142.50	$142.50	$142.50
Purchase #6	$173.25	10.284%	$191.067	$191.07	$191.05	$191.10
Purchase #7	$95.43	8.573%	$103.6112	$103.61	$103.60	$103.60
7 purchase totals =	$986.99		$1,077.4057	$1,077.40	$1,077.40	$1,077.40