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	$150.83	6.295%	$160.3247	$160.32	$160.30	$160.30
Purchase #2	$54.44	11.348%	$60.6179	$60.62	$60.60	$60.60
Purchase #3	$19.60	3.320%	$20.2507	$20.25	$20.25	$20.30
Purchase #4	$127.27	9.832%	$139.7832	$139.78	$139.80	$139.80
Purchase #5	$233.62	3.526%	$241.8574	$241.86	$241.85	$241.90
Purchase #6	$179.83	3.794%	$186.6528	$186.65	$186.65	$186.70
Purchase #7	$177.49	11.714%	$198.2812	$198.28	$198.30	$198.30
7 purchase totals =	$943.08		$1,007.7679	$1,007.76	$1,007.75	$1,007.90