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	$35.52	7.782%	$38.2842	$38.28	$38.30	$38.30
Purchase #2	$74.59	5.826%	$78.9356	$78.94	$78.95	$78.90
Purchase #3	$246.81	13.124%	$279.2013	$279.20	$279.20	$279.20
Purchase #4	$180.80	4.385%	$188.7281	$188.73	$188.75	$188.70
Purchase #5	$61.77	13.126%	$69.8779	$69.88	$69.90	$69.90
Purchase #6	$101.28	3.175%	$104.4956	$104.50	$104.50	$104.50
Purchase #7	$97.93	7.663%	$105.4344	$105.43	$105.45	$105.40
7 purchase totals =	$798.70		$864.9571	$864.96	$865.05	$864.90