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	$146.88	6.125%	$155.8764	$155.88	$155.90	$155.90
Purchase #2	$12.73	3.490%	$13.1743	$13.17	$13.15	$13.20
Purchase #3	$81.82	8.106%	$88.4523	$88.45	$88.45	$88.50
Purchase #4	$209.79	4.466%	$219.1592	$219.16	$219.15	$219.20
Purchase #5	$185.97	10.706%	$205.8799	$205.88	$205.90	$205.90
Purchase #6	$214.54	12.610%	$241.5935	$241.59	$241.60	$241.60
Purchase #7	$122.80	11.641%	$137.0951	$137.10	$137.10	$137.10
7 purchase totals =	$974.53		$1,061.2307	$1,061.23	$1,061.25	$1,061.40