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	$187.59	6.296%	$199.4007	$199.40	$199.40	$199.40
Purchase #2	$101.81	9.354%	$111.3333	$111.33	$111.35	$111.30
Purchase #3	$50.69	4.174%	$52.8058	$52.81	$52.80	$52.80
Purchase #4	$21.44	3.694%	$22.232	$22.23	$22.25	$22.20
Purchase #5	$210.38	3.588%	$217.9284	$217.93	$217.95	$217.90
Purchase #6	$32.84	9.498%	$35.9591	$35.96	$35.95	$36.00
Purchase #7	$116.32	6.120%	$123.4388	$123.44	$123.45	$123.40
7 purchase totals =	$721.07		$763.0981	$763.10	$763.15	$763.00