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	$75.94	8.557%	$82.4382	$82.44	$82.45	$82.40
Purchase #2	$237.59	8.304%	$257.3195	$257.32	$257.30	$257.30
Purchase #3	$169.60	9.331%	$185.4254	$185.43	$185.45	$185.40
Purchase #4	$59.95	4.852%	$62.8588	$62.86	$62.85	$62.90
Purchase #5	$210.40	8.812%	$228.9404	$228.94	$228.95	$228.90
Purchase #6	$116.48	6.848%	$124.4566	$124.46	$124.45	$124.50
Purchase #7	$118.35	13.585%	$134.4278	$134.43	$134.45	$134.40
7 purchase totals =	$988.31		$1,075.8667	$1,075.88	$1,075.90	$1,075.80