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	$6.94	10.130%	$7.643	$7.64	$7.65	$7.60
Purchase #2	$101.47	9.827%	$111.4415	$111.44	$111.45	$111.40
Purchase #3	$121.83	9.552%	$133.4672	$133.47	$133.45	$133.50
Purchase #4	$28.85	13.248%	$32.672	$32.67	$32.65	$32.70
Purchase #5	$95.26	6.618%	$101.5643	$101.56	$101.55	$101.60
Purchase #6	$121.62	5.719%	$128.5754	$128.58	$128.60	$128.60
Purchase #7	$216.48	10.242%	$238.6519	$238.65	$238.65	$238.70
7 purchase totals =	$692.45		$754.0153	$754.01	$754.00	$754.10