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	$247.93	6.762%	$264.695	$264.70	$264.70	$264.70
Purchase #2	$238.40	8.440%	$258.521	$258.52	$258.50	$258.50
Purchase #3	$112.28	5.144%	$118.0557	$118.06	$118.05	$118.10
Purchase #4	$144.92	9.543%	$158.7497	$158.75	$158.75	$158.70
Purchase #5	$94.70	11.808%	$105.8822	$105.88	$105.90	$105.90
Purchase #6	$32.53	9.192%	$35.5202	$35.52	$35.50	$35.50
Purchase #7	$84.65	13.235%	$95.8534	$95.85	$95.85	$95.90
7 purchase totals =	$955.41		$1,037.2772	$1,037.28	$1,037.25	$1,037.30