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	$99.95	11.528%	$111.4722	$111.47	$111.45	$111.50
Purchase #2	$152.83	7.769%	$164.7034	$164.70	$164.70	$164.70
Purchase #3	$71.60	5.578%	$75.5938	$75.59	$75.60	$75.60
Purchase #4	$55.78	3.240%	$57.5873	$57.59	$57.60	$57.60
Purchase #5	$205.78	9.832%	$226.0123	$226.01	$226.00	$226.00
Purchase #6	$11.28	12.671%	$12.7093	$12.71	$12.70	$12.70
Purchase #7	$85.99	11.143%	$95.5719	$95.57	$95.55	$95.60
7 purchase totals =	$683.21		$743.6502	$743.64	$743.60	$743.70