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	$5.67	13.661%	$6.4446	$6.44	$6.45	$6.40
Purchase #2	$173.60	13.138%	$196.4076	$196.41	$196.40	$196.40
Purchase #3	$175.51	6.758%	$187.371	$187.37	$187.35	$187.40
Purchase #4	$94.83	8.634%	$103.0176	$103.02	$103.00	$103.00
Purchase #5	$138.25	5.687%	$146.1123	$146.11	$146.10	$146.10
Purchase #6	$214.28	13.646%	$243.5206	$243.52	$243.50	$243.50
Purchase #7	$136.62	4.636%	$142.9537	$142.95	$142.95	$143.00
7 purchase totals =	$938.76		$1,025.8274	$1,025.82	$1,025.75	$1,025.80