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	$103.60	10.136%	$114.1009	$114.10	$114.10	$114.10
Purchase #2	$78.98	4.415%	$82.467	$82.47	$82.45	$82.50
Purchase #3	$128.57	11.632%	$143.5253	$143.53	$143.55	$143.50
Purchase #4	$78.96	4.725%	$82.6909	$82.69	$82.70	$82.70
Purchase #5	$116.42	5.604%	$122.9442	$122.94	$122.95	$122.90
Purchase #6	$12.68	11.242%	$14.1055	$14.11	$14.10	$14.10
Purchase #7	$141.34	6.296%	$150.2388	$150.24	$150.25	$150.20
7 purchase totals =	$660.55		$710.0726	$710.08	$710.10	$710.00