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	$228.74	11.298%	$254.583	$254.58	$254.60	$254.60
Purchase #2	$169.94	10.243%	$187.347	$187.35	$187.35	$187.30
Purchase #3	$236.60	11.578%	$263.9935	$263.99	$264.00	$264.00
Purchase #4	$221.61	5.406%	$233.5902	$233.59	$233.60	$233.60
Purchase #5	$47.62	8.195%	$51.5225	$51.52	$51.50	$51.50
Purchase #6	$234.61	12.587%	$264.1404	$264.14	$264.15	$264.10
Purchase #7	$42.59	6.485%	$45.352	$45.35	$45.35	$45.40
7 purchase totals =	$1,181.71		$1,300.5286	$1,300.52	$1,300.55	$1,300.50