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	$144.60	10.840%	$160.2746	$160.27	$160.25	$160.30
Purchase #2	$159.90	6.629%	$170.4998	$170.50	$170.50	$170.50
Purchase #3	$10.98	7.593%	$11.8137	$11.81	$11.80	$11.80
Purchase #4	$76.52	6.253%	$81.3048	$81.30	$81.30	$81.30
Purchase #5	$49.82	13.341%	$56.4665	$56.47	$56.45	$56.50
Purchase #6	$96.90	8.380%	$105.0202	$105.02	$105.00	$105.00
Purchase #7	$229.81	13.811%	$261.5491	$261.55	$261.55	$261.50
7 purchase totals =	$768.53		$846.9287	$846.92	$846.85	$846.90