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	$85.95	11.401%	$95.7492	$95.75	$95.75	$95.70
Purchase #2	$128.49	10.658%	$142.1845	$142.18	$142.20	$142.20
Purchase #3	$97.87	5.666%	$103.4153	$103.42	$103.40	$103.40
Purchase #4	$54.85	8.829%	$59.6927	$59.69	$59.70	$59.70
Purchase #5	$141.81	10.553%	$156.7752	$156.78	$156.80	$156.80
Purchase #6	$98.95	3.301%	$102.2163	$102.22	$102.20	$102.20
Purchase #7	$105.68	12.411%	$118.7959	$118.80	$118.80	$118.80
7 purchase totals =	$713.60		$778.8291	$778.84	$778.85	$778.80