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	$238.89	3.433%	$247.0911	$247.09	$247.10	$247.10
Purchase #2	$162.76	4.803%	$170.5774	$170.58	$170.60	$170.60
Purchase #3	$148.41	6.590%	$158.1902	$158.19	$158.20	$158.20
Purchase #4	$52.51	9.433%	$57.4633	$57.46	$57.45	$57.50
Purchase #5	$71.78	13.688%	$81.6052	$81.61	$81.60	$81.60
Purchase #6	$11.68	7.687%	$12.5778	$12.58	$12.60	$12.60
Purchase #7	$70.50	3.414%	$72.9069	$72.91	$72.90	$72.90
7 purchase totals =	$756.53		$800.4119	$800.42	$800.45	$800.50