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	$219.25	3.360%	$226.6168	$226.62	$226.60	$226.60
Purchase #2	$106.42	5.778%	$112.5689	$112.57	$112.55	$112.60
Purchase #3	$173.92	3.240%	$179.555	$179.56	$179.55	$179.60
Purchase #4	$147.61	13.572%	$167.6436	$167.64	$167.65	$167.60
Purchase #5	$177.88	4.209%	$185.367	$185.37	$185.35	$185.40
Purchase #6	$72.48	11.625%	$80.9058	$80.91	$80.90	$80.90
Purchase #7	$142.58	9.724%	$156.4445	$156.44	$156.45	$156.40
7 purchase totals =	$1,040.14		$1,109.1016	$1,109.11	$1,109.05	$1,109.10