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	$46.86	13.438%	$53.157	$53.16	$53.15	$53.20
Purchase #2	$75.45	6.518%	$80.3678	$80.37	$80.35	$80.40
Purchase #3	$208.96	9.556%	$228.9282	$228.93	$228.95	$228.90
Purchase #4	$65.83	8.792%	$71.6178	$71.62	$71.60	$71.60
Purchase #5	$64.25	10.667%	$71.1035	$71.10	$71.10	$71.10
Purchase #6	$235.59	10.239%	$259.7121	$259.71	$259.70	$259.70
Purchase #7	$246.35	3.646%	$255.3319	$255.33	$255.35	$255.30
7 purchase totals =	$943.29		$1,020.2183	$1,020.22	$1,020.20	$1,020.20