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	$176.94	4.284%	$184.5201	$184.52	$184.50	$184.50
Purchase #2	$131.30	11.633%	$146.5741	$146.57	$146.55	$146.60
Purchase #3	$213.25	10.198%	$234.9972	$235.00	$235.00	$235.00
Purchase #4	$168.89	4.298%	$176.1489	$176.15	$176.15	$176.10
Purchase #5	$146.30	13.685%	$166.3212	$166.32	$166.30	$166.30
Purchase #6	$19.83	3.118%	$20.4483	$20.45	$20.45	$20.40
Purchase #7	$113.35	4.363%	$118.2955	$118.30	$118.30	$118.30
7 purchase totals =	$969.86		$1,047.3053	$1,047.31	$1,047.25	$1,047.20