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	$227.40	4.578%	$237.8104	$237.81	$237.80	$237.80
Purchase #2	$78.31	10.829%	$86.7902	$86.79	$86.80	$86.80
Purchase #3	$34.86	6.321%	$37.0635	$37.06	$37.05	$37.10
Purchase #4	$98.60	12.351%	$110.7781	$110.78	$110.80	$110.80
Purchase #5	$196.31	4.827%	$205.7859	$205.79	$205.80	$205.80
Purchase #6	$244.83	4.730%	$256.4105	$256.41	$256.40	$256.40
Purchase #7	$231.52	3.291%	$239.1393	$239.14	$239.15	$239.10
7 purchase totals =	$1,111.83		$1,173.7779	$1,173.78	$1,173.80	$1,173.80