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	$241.80	8.581%	$262.5489	$262.55	$262.55	$262.50
Purchase #2	$223.93	4.402%	$233.7874	$233.79	$233.80	$233.80
Purchase #3	$16.57	11.703%	$18.5092	$18.51	$18.50	$18.50
Purchase #4	$101.87	12.848%	$114.9583	$114.96	$114.95	$115.00
Purchase #5	$82.52	9.732%	$90.5508	$90.55	$90.55	$90.60
Purchase #6	$112.36	13.255%	$127.2533	$127.25	$127.25	$127.30
Purchase #7	$67.99	8.785%	$73.9629	$73.96	$73.95	$74.00
7 purchase totals =	$847.04		$921.5708	$921.57	$921.55	$921.70