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	$45.25	7.684%	$48.727	$48.73	$48.75	$48.70
Purchase #2	$13.52	10.485%	$14.9376	$14.94	$14.95	$14.90
Purchase #3	$29.48	10.152%	$32.4728	$32.47	$32.45	$32.50
Purchase #4	$52.80	5.344%	$55.6216	$55.62	$55.60	$55.60
Purchase #5	$39.98	6.541%	$42.5951	$42.60	$42.60	$42.60
Purchase #6	$144.53	4.410%	$150.9038	$150.90	$150.90	$150.90
Purchase #7	$27.52	4.550%	$28.7722	$28.77	$28.75	$28.80
7 purchase totals =	$353.08		$374.0301	$374.03	$374.00	$374.00