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	$74.89	4.341%	$78.141	$78.14	$78.15	$78.10
Purchase #2	$156.29	11.390%	$174.0914	$174.09	$174.10	$174.10
Purchase #3	$192.77	4.814%	$202.0499	$202.05	$202.05	$202.00
Purchase #4	$200.39	5.848%	$212.1088	$212.11	$212.10	$212.10
Purchase #5	$30.77	13.610%	$34.9578	$34.96	$34.95	$35.00
Purchase #6	$92.58	6.383%	$98.4894	$98.49	$98.50	$98.50
Purchase #7	$103.70	7.629%	$111.6113	$111.61	$111.60	$111.60
7 purchase totals =	$851.39		$911.4496	$911.45	$911.45	$911.40