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	$42.72	4.437%	$44.6155	$44.62	$44.60	$44.60
Purchase #2	$216.90	4.469%	$226.5933	$226.59	$226.60	$226.60
Purchase #3	$43.95	10.864%	$48.7247	$48.72	$48.70	$48.70
Purchase #4	$197.94	10.357%	$218.4406	$218.44	$218.45	$218.40
Purchase #5	$49.69	8.427%	$53.8774	$53.88	$53.90	$53.90
Purchase #6	$52.27	4.307%	$54.5213	$54.52	$54.50	$54.50
Purchase #7	$92.37	13.456%	$104.7993	$104.80	$104.80	$104.80
7 purchase totals =	$695.84		$751.5721	$751.57	$751.55	$751.50