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	$229.67	3.503%	$237.7153	$237.72	$237.70	$237.70
Purchase #2	$37.45	9.279%	$40.925	$40.93	$40.95	$40.90
Purchase #3	$75.84	3.442%	$78.4504	$78.45	$78.45	$78.50
Purchase #4	$52.67	5.786%	$55.7175	$55.72	$55.70	$55.70
Purchase #5	$228.72	5.304%	$240.8513	$240.85	$240.85	$240.90
Purchase #6	$32.65	7.589%	$35.1278	$35.13	$35.15	$35.10
Purchase #7	$28.60	5.222%	$30.0935	$30.09	$30.10	$30.10
7 purchase totals =	$685.60		$718.8808	$718.89	$718.90	$718.90