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	$10.61	11.723%	$11.8538	$11.85	$11.85	$11.90
Purchase #2	$171.35	7.530%	$184.2527	$184.25	$184.25	$184.30
Purchase #3	$250.40	13.580%	$284.4043	$284.40	$284.40	$284.40
Purchase #4	$15.76	12.693%	$17.7604	$17.76	$17.75	$17.80
Purchase #5	$156.39	12.287%	$175.6056	$175.61	$175.60	$175.60
Purchase #6	$82.78	7.724%	$89.1739	$89.17	$89.15	$89.20
Purchase #7	$243.94	10.625%	$269.8586	$269.86	$269.85	$269.90
7 purchase totals =	$931.23		$1,032.9093	$1,032.90	$1,032.85	$1,033.10