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	$186.67	4.135%	$194.3888	$194.39	$194.40	$194.40
Purchase #2	$39.54	3.429%	$40.8958	$40.90	$40.90	$40.90
Purchase #3	$215.60	13.158%	$243.9686	$243.97	$243.95	$244.00
Purchase #4	$184.71	9.848%	$202.9002	$202.90	$202.90	$202.90
Purchase #5	$112.46	5.653%	$118.8174	$118.82	$118.80	$118.80
Purchase #6	$225.57	13.288%	$255.5437	$255.54	$255.55	$255.50
Purchase #7	$85.86	5.262%	$90.378	$90.38	$90.40	$90.40
7 purchase totals =	$1,050.41		$1,146.8925	$1,146.90	$1,146.90	$1,146.90