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	$188.72	6.255%	$200.5244	$200.52	$200.50	$200.50
Purchase #2	$208.80	7.504%	$224.4684	$224.47	$224.45	$224.50
Purchase #3	$26.37	3.588%	$27.3162	$27.32	$27.30	$27.30
Purchase #4	$56.57	13.446%	$64.1764	$64.18	$64.20	$64.20
Purchase #5	$13.75	5.461%	$14.5009	$14.50	$14.50	$14.50
Purchase #6	$5.91	6.404%	$6.2885	$6.29	$6.30	$6.30
Purchase #7	$145.93	6.632%	$155.6081	$155.61	$155.60	$155.60
7 purchase totals =	$646.05		$692.8829	$692.89	$692.85	$692.90