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	$228.58	13.845%	$260.2269	$260.23	$260.25	$260.20
Purchase #2	$233.82	13.154%	$264.5767	$264.58	$264.60	$264.60
Purchase #3	$216.78	3.872%	$225.1737	$225.17	$225.15	$225.20
Purchase #4	$96.74	11.796%	$108.1515	$108.15	$108.15	$108.20
Purchase #5	$29.78	10.575%	$32.9292	$32.93	$32.95	$32.90
Purchase #6	$160.80	7.802%	$173.3456	$173.35	$173.35	$173.30
Purchase #7	$137.66	10.427%	$152.0138	$152.01	$152.00	$152.00
7 purchase totals =	$1,104.16		$1,216.4174	$1,216.42	$1,216.45	$1,216.40