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	$102.58	6.394%	$109.139	$109.14	$109.15	$109.10
Purchase #2	$206.37	11.475%	$230.051	$230.05	$230.05	$230.10
Purchase #3	$132.52	13.514%	$150.4288	$150.43	$150.45	$150.40
Purchase #4	$141.44	6.382%	$150.4667	$150.47	$150.45	$150.50
Purchase #5	$183.31	5.668%	$193.7	$193.70	$193.70	$193.70
Purchase #6	$246.96	3.441%	$255.4579	$255.46	$255.45	$255.50
Purchase #7	$167.34	10.134%	$184.2982	$184.30	$184.30	$184.30
7 purchase totals =	$1,180.52		$1,273.5416	$1,273.55	$1,273.55	$1,273.60