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	$196.95	9.844%	$216.3378	$216.34	$216.35	$216.30
Purchase #2	$246.67	9.646%	$270.4638	$270.46	$270.45	$270.50
Purchase #3	$50.45	7.719%	$54.3442	$54.34	$54.35	$54.30
Purchase #4	$99.92	11.334%	$111.2449	$111.24	$111.25	$111.20
Purchase #5	$127.74	11.333%	$142.2168	$142.22	$142.20	$142.20
Purchase #6	$9.84	11.836%	$11.0047	$11.00	$11.00	$11.00
Purchase #7	$166.53	6.622%	$177.5576	$177.56	$177.55	$177.60
7 purchase totals =	$898.10		$983.1698	$983.16	$983.15	$983.10