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	$49.80	3.804%	$51.6944	$51.69	$51.70	$51.70
Purchase #2	$215.88	13.240%	$244.4625	$244.46	$244.45	$244.50
Purchase #3	$96.76	3.617%	$100.2598	$100.26	$100.25	$100.30
Purchase #4	$219.39	8.577%	$238.2071	$238.21	$238.20	$238.20
Purchase #5	$213.64	6.404%	$227.3215	$227.32	$227.30	$227.30
Purchase #6	$198.52	5.784%	$210.0024	$210.00	$210.00	$210.00
Purchase #7	$81.60	9.382%	$89.2557	$89.26	$89.25	$89.30
7 purchase totals =	$1,075.59		$1,161.2034	$1,161.20	$1,161.15	$1,161.30