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	$182.94	7.511%	$196.6806	$196.68	$196.70	$196.70
Purchase #2	$122.60	11.784%	$137.0472	$137.05	$137.05	$137.00
Purchase #3	$178.98	9.615%	$196.1889	$196.19	$196.20	$196.20
Purchase #4	$49.93	4.335%	$52.0945	$52.09	$52.10	$52.10
Purchase #5	$203.83	9.455%	$223.1021	$223.10	$223.10	$223.10
Purchase #6	$123.89	10.869%	$137.3556	$137.36	$137.35	$137.40
Purchase #7	$133.65	9.679%	$146.586	$146.59	$146.60	$146.60
7 purchase totals =	$995.82		$1,089.0549	$1,089.06	$1,089.10	$1,089.10