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	$112.37	13.774%	$127.8478	$127.85	$127.85	$127.80
Purchase #2	$12.59	12.627%	$14.1797	$14.18	$14.20	$14.20
Purchase #3	$196.71	11.589%	$219.5067	$219.51	$219.50	$219.50
Purchase #4	$250.88	9.427%	$274.5305	$274.53	$274.55	$274.50
Purchase #5	$119.50	3.640%	$123.8498	$123.85	$123.85	$123.80
Purchase #6	$51.42	4.151%	$53.5544	$53.55	$53.55	$53.60
Purchase #7	$220.32	7.867%	$237.6526	$237.65	$237.65	$237.70
7 purchase totals =	$963.79		$1,051.1215	$1,051.12	$1,051.15	$1,051.10