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	$225.60	7.187%	$241.8139	$241.81	$241.80	$241.80
Purchase #2	$158.76	8.766%	$172.6769	$172.68	$172.70	$172.70
Purchase #3	$152.79	12.432%	$171.7849	$171.78	$171.80	$171.80
Purchase #4	$81.70	13.190%	$92.4762	$92.48	$92.50	$92.50
Purchase #5	$195.67	8.125%	$211.5682	$211.57	$211.55	$211.60
Purchase #6	$176.51	7.816%	$190.306	$190.31	$190.30	$190.30
Purchase #7	$109.82	9.116%	$119.8312	$119.83	$119.85	$119.80
7 purchase totals =	$1,100.85		$1,200.4573	$1,200.46	$1,200.50	$1,200.50