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	$52.59	9.267%	$57.4635	$57.46	$57.45	$57.50
Purchase #2	$99.49	10.451%	$109.8877	$109.89	$109.90	$109.90
Purchase #3	$27.71	6.135%	$29.41	$29.41	$29.40	$29.40
Purchase #4	$109.96	5.644%	$116.1661	$116.17	$116.15	$116.20
Purchase #5	$22.32	6.609%	$23.7951	$23.80	$23.80	$23.80
Purchase #6	$47.62	13.601%	$54.0968	$54.10	$54.10	$54.10
Purchase #7	$218.33	9.376%	$238.8006	$238.80	$238.80	$238.80
7 purchase totals =	$578.02		$629.6198	$629.63	$629.60	$629.70